Applications of non-collinearly coupled magnetic layers

ABSTRACT

A magnetic device comprising having a first magnetic layer having a first magnetization direction, a second magnetic layer having a second magnetization direction, a first coupling layer interposed between the first and second magnetic layers, a third magnetic layer having a third magnetization direction, a first magnetoresistive layer interposed between the third magnetic layer and the second magnetic layer, and a circuit connected to one or more of the layers of the magnetic device by at least a pair of leads. The circuit is configured to determine a change in resistance between the pair of leads. The change in resistance is based at least in part on a change in an angular relationship between the third magnetization direction and the second magnetization direction caused by an external magnetic field or a current passing through at least a portion of the device.

RELATED APPLICATIONS

This application is a continuation-in-part of Patent Cooperation Treatyapplication No. PCT/CA2017/051419 filed 24 Nov. 2017 which in turnclaims priority (and the benefit under 35 USC 119) from U.S. applicationNo. 62/555,625 filed 7 Sep. 2017 and U.S. application No. 62/470,123filed 10 Mar. 2017. This application itself also claims priority (andthe benefit under 35 USC 119) from U.S. application No. 62/614,928 filed8 Jan. 2018, U.S. application No. 62/555,625 filed 7 Sep. 2017 and U.S.application No. 62/470,123 filed 10 Mar. 2017. All of the applicationsreferred to in this paragraph are hereby incorporated herein byreference.

TECHNICAL FIELD

This invention relates to magnetic coupling layers, devices comprisingmagnetic coupling layers, applications of magnetic coupling layers andmethods for fabricating and/or using same. Particular embodimentsprovide devices comprising one or more coupling layers for spacing aparta plurality of magnetic layers and for aligning magnetization directionsof one or more of the plurality of magnetic layers at non-collinearangles relative to one another.

BACKGROUND

Structures comprising two or more magnetic layers that are coupled viaan intervening coupling layer may be employed for magnetic memorydevices, magnetic sensors (e.g. magnetoresistive sensors), and/or otherapplications. Typically, the magnetic moments (or magnetic directions ormagnetization directions) of such magnetic layers are coupled at 0°relative to one another (which may be referred to as beingferromagnetically coupled) or are coupled at 180° relative to oneanother (which may be referred to as being antiferromagnetically coupledand/or as antiparallel coupling). While ferromagnetically coupledmagnetic layers and antiferromagnetically coupled layers have proven tobe useful, there are a number of drawbacks associated with having themagnetic layers coupled at 0° relative to one another. For example, formagnetoresistive sensor applications, such as those employingtunnel-magnetoresistance (TMR) or giant-magnetoresistance (GMR), suchdrawbacks include, without limitation: ambiguities in the resistiveresponse to the directionality of the applied field and non-linearity ofthe resistive response to the applied field. As another example, formemory device applications, switching between stable states is typicallyreliant on probabilistic thermal variation, leading to drawbacks thatinclude, without limitation: undesirably long switching times,undesirably high error rates and undesirably high switching current orswitching power.

U.S. Pat. No. 7,199,984 discloses a PtMn coupling layer having an atomicconcentration of 25-75% Pt and 25-75% Mn for coupling CoFe or NiFemagnetic layers with orthogonally oriented magnetization directions.Such orthogonally oriented magnetization directions represent an exampleof non-collinearly coupled (NCC) magnetic layers.

The PtMn coupling layer disclosed by U.S. Pat. No. 7,199,984 has athickness of less than 10 nm and is preferably between 1.5 and 5.0 nm.PtMn coupling layers of the type disclosed by U.S. Pat. No. 7,199,984have weak coupling strength and low saturation fields. Because of thisweak coupling strength, sensors which employ coupling layers constructedaccording to the teachings of U.S. Pat. No. 7,199,984 may only beemployed for sensing external magnetic fields less than approximately1000 Oe. There is a desire for magnetic sensors with the ability tosense stronger external magnetic fields. In addition, PtMn couplinglayers of the type disclosed by U.S. Pat. No. 7,199,984 have beendetermined to require thicknesses of greater than about 1.2 nm. Belowthis thickness, diffusion of material from the adjacent magnetic layersdestroys the orthogonal non-collinear coupling. There is a generaldesire to make magnetic structures (e.g. non-collinearly coupledmagnetic structures) that are as small as is reasonably possible.

Still further, the coupling layers disclosed by U.S. Pat. No. 7,199,984tend to revert to coupling at 0° after annealing (e.g. at temperaturesgreater than 200° C. or even at lower temperatures). For example, theinventors created a structure according to the teachings of U.S. Pat.No. 7,199,984 where a Mn coupling layer having a thickness of 1.4 nm wasinterposed between Co magnetic layers. FIG. 1 shows the normalizedmagnetization of this structure as a function of external magnetic fieldH without annealing (dark circles) and with annealing at 200° C. (opencircles). As can be seen from FIG. 1, the magnetic structure having acoupling layer of Mn that is annealed at 200° C. does not exhibitnon-collinear magnetic coupling between the Co magnetic layers of themagnetic structure (e.g. the annealed magnetic structure is fullysaturated even with a very small applied magnetic field (e.g. 100 Oe)).Many applications for coupled magnetic layers, such as applicationswhich make use of the tunnel magnetoresistance (TMR) effect, requireannealing (e.g. at temperatures greater than 200° C.) to increasesensitivity and increase the magnitude of resistance changes across amagnetoresistive layer. Annealing may also be required to alignantiferromagnetic layers in particular applications. There is a generaldesire for magnetic structures comprising two or more magnetic layersthat are coupled via an intervening coupling layer where the magneticstructure, or a portion thereof may be annealed (for example, attemperatures above 200° C.) without undesirably affecting the coupling(e.g. non-collinear coupling) of the two or more magnetic structures.Structures fabricated according to the techniques described in U.S. Pat.No. 7,199,984 exhibit non-collinear coupling at 90° only. There is ageneral desire to provide structures that exhibit non-collinear couplingat angles other than 90°.

U.S. Pat. No. 6,893,741 discloses a RuFe coupling layer having an atomicconcentration of less than or equal to 60% Fe and at least 40% Ru forantiferromagnetically coupling specific Co alloy (such as CoPtCrB)magnetic layers (i.e. with magnetization directions at an angle of 180°with respect to one another). U.S. Pat. No. 6,893,741 discloses anexchange field (also commonly referred to as a saturation field) of 2750Oe for Ru₆₅Fe₃₅ as compared to 1575 Oe for a pure Ru coupling layer. Tothe extent that the assertions in U.S. Pat. No. 6,893,741 are accurate,such structures could only be employed for sensing external magneticfields under less than approximately 1375 Oe. There is a desire formagnetic sensors with the ability to sense stronger external magneticfields, whether such sensors comprise antiferromagnetically coupledmagnetic layers and/or non-collinearly coupled magnetic layers.Similarly, the coupling layers disclosed by U.S. Pat. No. 6,893,741could not be employed for the purpose of pinning a magnetic layer inapplications where external fields of greater than 2750 Oe may beexperienced. Further, the coupling layers disclosed by U.S. Pat. No.6,893,741 do not allow coupling at angles other than 180° and,consequently, suffer from the above-described drawbacks ofantiferromagnetic coupling.

There is a general desire for magnetic devices comprising couplinglayers for coupling magnetic layers at non-collinear angles (i.e. anglesgreater than 0° and less than 180°). It may be desirable for suchmagnetic devices to have high coupling strength and/or high saturationfields. There is a general desire for magnetic devices comprisingcoupling layers for coupling magnetic layers at non-collinear anglesother than 90° (i.e. angles other than 0°, 90° and 180°). There is ageneral desire for magnetic devices comprising coupling layers forcoupling magnetic layers at non-collinear angles (i.e. angles other than0° and 180°) after annealing. There is a general desire for magneticdevices comprising coupling layers that are practical to manufacturewithout requiring overly stringent tolerances on atomic composition andatomic distribution and coupling layer thickness.

The foregoing examples of the related art and limitations relatedthereto are intended to be illustrative and not exclusive. Otherlimitations of the related art will become apparent to those of skill inthe art upon a reading of the specification and a study of the drawings.

SUMMARY

The following embodiments and aspects thereof are described andillustrated in conjunction with systems, tools and methods which aremeant to be exemplary and illustrative, not limiting in scope. Invarious embodiments, one or more of the above-described problems havebeen reduced or eliminated, while other embodiments are directed toother improvements.

An aspect of the invention provides a magnetic device having a firstmagnetic layer having a first magnetization direction and a secondmagnetic layer having a second magnetization direction. The secondmagnetic layer is spaced apart from the first magnetic layer in the Zdirection. A first coupling layer is interposed between the first andsecond magnetic layers. The first magnetic layer is non-collinearlycoupled to the second magnetic layer by the first coupling layer suchthat, in the absence of external magnetic field, the first magnetizationdirection is oriented at a first non-collinear angle relative to thesecond magnetization direction. The magnetic device also has a thirdmagnetic layer having a third magnetization direction and a firstmagnetoresistive layer interposed between the third magnetic layer andthe second magnetic layer. A circuit is connected to one or more of thelayers of the magnetic device by at least a pair of leads. The circuitis configured to determine a change in resistance between the pair ofleads. The change in resistance is based at least in part on a change inan angular relationship between the third magnetization direction andthe second magnetization direction caused by application of an externalmagnetic field in a region where at least a portion of the device islocated or by a current passing through at least a portion of thedevice. An X direction is orthogonal to the Z direction and a Ydirection is orthogonal to the X direction and to the Z direction.

In some embodiments, the first coupling layer comprises at least onefirst non-magnetic element selected from the group consisting of: Ag,Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re, Os, Au, Al and Si, and atleast one first magnetic element selected from the group consisting of:Ni, Co, and Fe. An atomic ratio of the at least one first non-magneticelement to the at least one first magnetic element is (100-x):x where xis an atomic concentration parameter which causes, or is selected tocause, the first magnetic layer to be non-collinearly coupled to thesecond magnetic layer.

In some embodiments, the coupling layer has a thickness, t_(c), andwherein the combination of the atomic concentration parameter x and thecoupling layer thickness t_(c) causes, or is selected to cause, thefirst magnetic layer to be non-collinearly coupled to the secondmagnetic layer. In some embodiments, the first magnetic layer has athickness, t_(m1), and the second magnetic layer has a thickness,t_(m2), and t_(m1) and t_(m2) are each selected such that the firstmagnetic layer is non-collinearly coupled to the second magnetic layer.

In some embodiments, the first non-collinear angle is betweenapproximately 5° and 175° in absence of external magnetic field. In someembodiments, the first non-collinear angle is a non-orthogonal,non-collinear angle between approximately 5° and 85° or 95° and 175° inabsence of external magnetic field. In some embodiments, the firstnon-collinear angle is a non-orthogonal, non-collinear angle betweenapproximately 95° and 175° in absence of external magnetic field.

In some embodiments, the first magnetization direction is fixed, thesecond magnetization direction is free and the third magnetizationdirection is fixed. In some embodiments, the first magnetizationdirection is fixed, the second magnetization direction is fixed and thethird magnetization direction is free. In some embodiments, the firstmagnetization direction is free, the second magnetization direction isfree and the third magnetization direction is fixed.

In some embodiments, the at least a pair of leads are connected acrossthe first, second and third magnetic layers, the first coupling layerand the first magnetoresistive layer.

In some embodiments, a second coupling layer interposed between thefirst magnetic layer and a fourth magnetic layer, the fourth magneticlayer having a fourth magnetization direction. In some embodiments, theat least a pair of leads are connected across the first, second, thirdand fourth magnetic layers, the first and second coupling layers and thefirst magnetoresistive layer. In some embodiments, the first magneticlayer is non-collinearly coupled to the fourth magnetic layer such that,in the absence of external magnetic field, the first magnetizationdirection is oriented at a second non-collinear angle relative to thefourth magnetization direction. In some embodiments, the fourthmagnetization direction is fixed.

In some embodiments, the second coupling layer comprises at least onesecond non-magnetic element selected from the group consisting of: Ag,Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re, Os, Au, Al and Si, and atleast one second magnetic element selected from the group consisting of:Ni, Co, and Fe. An atomic ratio of the at least one second non-magneticelement to the at least one second magnetic element is (100-x):x, wherex is an atomic concentration parameter which causes, or is selected tocause, the first magnetic layer to be non-collinearly coupled to thefourth magnetic layer such that, in the absence of external magneticfield, the first magnetization direction is oriented at the secondnon-collinear angle relative to the fourth magnetization direction.

In some embodiments, a second magnetoresistive layer is interposedbetween the first magnetic layer and a fourth magnetic layer, the fourthmagnetic layer having a fourth magnetization direction. In someembodiments, the at least a pair of leads are connected across thefirst, second, third and fourth magnetic layers, the first couplinglayer and the first and second magnetoresistive layers. In someembodiments, the fourth magnetization direction is fixed.

In some embodiments, a second magnetoresistive layer is interposedbetween a fourth magnetic layer and the third magnetic layer, the fourthmagnetic layer having a fourth magnetization direction and a secondcoupling layer is interposed between the fourth magnetic layer and afifth magnetic layer, the fifth magnetic layer having a fifthmagnetization direction and the fourth and fifth magnetizationdirections are fixed to one another. In some embodiments, the at least apair of leads are connected across the first, second, third, fourth andfifth magnetic layers, the first and second coupling layers and thefirst and second magnetoresistive layers. In some embodiments, the fifthmagnetic layer is non-collinearly coupled to the fourth magnetic layersuch that, in the absence of external magnetic field, the fifthmagnetization direction is oriented at a second non-collinear anglerelative to the fourth magnetization direction.

In some embodiments, the second coupling layer comprises at least onesecond non-magnetic element selected from the group consisting of: Ag,Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re, Os, Au, Al and Si, and atleast one second magnetic element selected from the group consisting of:Ni, Co, and Fe. An atomic ratio of the at least one second non-magneticelement to the at least one second magnetic element is (100-x):x, wherex is an atomic concentration parameter which causes, or is selected tocause, the first magnetic layer to be non-collinearly coupled to thefourth magnetic layer such that, in the absence of external magneticfield, the first magnetization direction is oriented at the secondnon-collinear angle relative to the fourth magnetization direction.

In some embodiments, the second and fourth magnetization directions eachhave non-zero Z direction components or non-zero Y direction components.In some embodiments, the second magnetization direction has an Xdirection component oriented in the opposite direction of an X directioncomponent of the fourth magnetization direction. In some embodiments,the second magnetization direction has a Y direction component orientedin the opposite direction of a Y direction component of the fourthmagnetization direction. In some embodiments, the second magnetizationdirection has a Z direction component oriented in the opposite directionof a Z direction component of the fourth magnetization direction. Insome embodiments, the third magnetization direction is parallel to the Zdirection. In some embodiments, the third magnetization directionextends in a plane defined by the X and Y directions.

In some embodiments, at least a portion of the magnetic device has an Xdirection dimension that is greater than a Y direction dimension of theat least a portion of the magnetic device. In some embodiments, the Xdirection dimension is at least double the Y direction dimension. Insome embodiments, at least a portion of the magnetic device has an Xdirection dimension that is substantially equal to a Y directiondimension of the at least a portion of the magnetic device. In someembodiments, at least a portion of the magnetic device has an Xdirection dimension that is within 0.9 to 1.1 times the size of a Ydirection dimension of the at least a portion of the magnetic device.

In some embodiments, a magnetic device discussed herein is part of amagnetic memory device and the change in resistance is based at least inpart on the change in the angular relationship between the thirdmagnetization direction and the second magnetization direction caused bya current passing through at least a portion of the device. In someembodiments, the change in the angular relationship between the thirdmagnetization direction and the second magnetization comprises a changebetween a first state representing a first value for a bit ofinformation and a second state representing a second value for the bitof information. In some embodiments, information may be stored on themagnetic memory device by applying a current through at least a portionof the device to change the angular relationship between the thirdmagnetization direction and the second magnetization direction,measuring the resistance of the magnetic device to determine the angularrelationship between the third magnetization direction and the secondmagnetization direction, and associating a measured relationship betweenthe third magnetization direction and the second magnetization directionwith a value of a bit of information.

In some embodiments, a magnetic device discussed herein is part of amagnetic sensor and the change in resistance is based at least in parton the change in the angular relationship between the thirdmagnetization direction and the second magnetization direction caused bythe application of the external magnetic field. In some embodiments, anexternal field may be sensed by a magnetic sensor device by applying anexternal field to the magnetic device, measuring the resistance of themagnetic device to determine the angular relationship between the thirdmagnetization direction and the second magnetization direction, andassociating a measured relationship between the third magnetizationdirection and the second magnetization direction with the presence ofthe external field.

In some embodiments, associating the measured relationship between thethird magnetization direction and the second magnetization directionwith the presence of the external field comprises associating themeasured relationship between the third magnetization direction and thesecond magnetization direction with a magnitude of the external field.In some embodiments, associating the measured relationship between thethird magnetization direction and the second magnetization directionwith the presence of the external field comprises associating themeasured relationship between the third magnetization direction and thesecond magnetization direction with a direction of the external field.

In some embodiments, a magnetic device discussed herein is part of anoscillator device and a driver circuit is connected to one or more ofthe layers of the magnetic device to apply driver current to themagnetic device to create, in the circuit, a signal based at least inpart on the angular relationship between the third magnetizationdirection and the second magnetization direction. In some embodiments,the driver current is direct current or alternating current and thesignal is a direct current signal or an alternating current signal. Insome embodiments, an external magnetic field may be sensed with theoscillator device by applying an external field to the oscillatordevice, measuring the signal and associating a measurement of the signalwith the presence of the external field. In some embodiments,associating the measurement of the signal with the presence of theexternal field comprises associating the measurement of the signal witha magnitude of the external field. In some embodiments, associating themeasurement of the signal with the presence of the external fieldcomprises associating the measurement of the signal with a direction ofthe external field. In some embodiments, the measurement of the signalrepresents an amplitude of the signal. In some embodiments, themeasurement of the signal represents a frequency of the signal.

In some embodiments, an alternating current output signal may be createdfrom a direct current input signal with a magnetic device by applying adirect current input signal through one or more layers of the magneticdevice to continuously change the angular relationship between the thirdmagnetization direction and the second magnetization direction, andreceiving an alternating current output signal based at least in part onthe continuous change of the angular relationship between the thirdmagnetization direction and the second magnetization direction.

In some embodiments, a direct current output signal may be created froman alternating current input signal using a magnetic device by applyingan alternating current input signal through one or more layers of themagnetic device to continuously change the angular relationship betweenthe third magnetization direction and the second magnetizationdirection, and receiving a direct current output signal based at leastin part on the continuous change of the angular relationship between thethird magnetization direction and the second magnetization direction.

Another aspect of the invention provides a magnetic device having anupper magnetic layer having an upper magnetization direction, a lowermagnetic layer having a lower magnetization direction, the lowermagnetic layer spaced apart from the upper magnetic layer in a Zdirection, an interior magnetic layer having an interior magnetizationdirection, a lower magnetoresistive layer interposed between the lowermagnetic layer and the interior magnetic layer and an uppermagnetoresistive layer interposed between the upper magnetic layer andthe free magnetic layer. A circuit is connected to one or more of thelayers of the magnetic device by at least a pair of leads. The circuitis configured to determine a change in resistance between the pair ofleads, the change in resistance based at least in part on a change in anangular relationship between the upper magnetization direction and theinterior magnetization and an angular relationship between the lowermagnetization direction and the interior magnetization direction causedby application of an external magnetic field in a region where at leasta portion of the device is located or by a current passing through atleast a portion of the device. An X direction is orthogonal to the Zdirection and a Y direction is orthogonal to the X direction and to theZ direction. The upper and lower magnetization directions are each fixedand the interior magnetization direction is free. The upper and lowermagnetization directions each have non-zero Z direction components ornon-zero Y components in the absence of an external magnetic field. Theupper magnetization direction has an X direction component oriented inthe opposite direction of an X direction component of the lowermagnetization direction.

In some embodiments, the at least a pair of leads are connected acrossthe upper, lower and interior magnetic layers and the upper and lowermagnetoresistive layers. In some embodiments, the upper magnetizationdirection has a Y direction component oriented in the opposite directionof a Y direction component of the lower magnetization direction. In someembodiments, the upper magnetization direction has a Z directioncomponent oriented in the opposite direction of a Z direction componentof the lower magnetization direction. In some embodiments, the interiormagnetization direction is parallel to the Z direction in the absence ofthe external magnetic field. In some embodiments, the interiormagnetization direction extends in a plane defined by the X and Ydirections in the absence of the external magnetic field.

Another aspect of the invention provides a magnetic memory device havinga first magnetic layer having a first magnetization direction and asecond magnetic layer having a second magnetization direction. Thesecond magnetic layer is spaced apart from the first magnetic layer inthe Z direction. A first coupling layer is interposed between the firstand second magnetic layers. The first magnetic layer is non-collinearlycoupled to the second magnetic layer by the first coupling layer suchthat, in the absence of external magnetic field, the first magnetizationdirection is oriented at a first non-collinear angle relative to thesecond magnetization direction. The magnetic memory device also hasthird magnetic layer having a third magnetization direction. A firstmagnetoresistive layer is interposed between the third magnetic layerand the second magnetic layer. A circuit is connected to one or more ofthe layers of the magnetic device by at least a pair of leads. Thecircuit is configured to determine a change in resistance between thepair of leads wherein the change in resistance is based at least in parton the change in the angular relationship between the thirdmagnetization direction and the second magnetization direction caused bya current passing through at least a portion of the device. An Xdirection is orthogonal to the Z direction and a Y direction isorthogonal to the X direction and to the Z direction.

Another aspect of the invention provides a magnetic sensor device havinga first magnetic layer having a first magnetization direction and asecond magnetic layer having a second magnetization direction. Thesecond magnetic layer is spaced apart from the first magnetic layer inthe Z direction. A first coupling layer is interposed between the firstand second magnetic layers. The first magnetic layer is non-collinearlycoupled to the second magnetic layer by the first coupling layer suchthat, in the absence of external magnetic field, the first magnetizationdirection is oriented at a first non-collinear angle relative to thesecond magnetization direction. The magnetic memory device also hasthird magnetic layer having a third magnetization direction. A firstmagnetoresistive layer is interposed between the third magnetic layerand the second magnetic layer. A circuit is connected to one or more ofthe layers of the magnetic device by at least a pair of leads. Thecircuit is configured to determine a change in resistance between thepair of leads, wherein the change in resistance is based at least inpart on the change in the angular relationship between the thirdmagnetization direction and the second magnetization direction caused bythe application of the external magnetic field. An X direction isorthogonal to the Z direction and a Y direction is orthogonal to the Xdirection and to the Z direction.

Another aspect of the invention provides an oscillator device having afirst magnetic layer having a first magnetization direction and a secondmagnetic layer having a second magnetization direction. The secondmagnetic layer is spaced apart from the first magnetic layer in the Zdirection. A first coupling layer is interposed between the first andsecond magnetic layers. The first magnetic layer is non-collinearlycoupled to the second magnetic layer by the first coupling layer suchthat, in the absence of external magnetic field, the first magnetizationdirection is oriented at a first non-collinear angle relative to thesecond magnetization direction. The magnetic memory device also hasthird magnetic layer having a third magnetization direction. A firstmagnetoresistive layer is interposed between the third magnetic layerand the second magnetic layer. A driver circuit is connected to one ormore of the layers of the magnetic device to apply driver current to themagnetic device to create a signal based at least in part on an angularrelationship between the third magnetization direction and the secondmagnetization direction. An X direction is orthogonal to the Z directionand a Y direction is orthogonal to the X direction and to the Zdirection.

Another aspect of the invention provides method of sensing an externalfield with a magnetic sensor device. The method includes providing anoscillator device comprising. The oscillator device has a first magneticlayer having a first magnetization direction and a second magnetic layerhaving a second magnetization direction. The second magnetic layer isspaced apart from the first magnetic layer in the Z direction. A firstcoupling layer is interposed between the first and second magneticlayers. The first magnetic layer is non-collinearly coupled to thesecond magnetic layer by the first coupling layer such that, in theabsence of external magnetic field, the first magnetization direction isoriented at a first non-collinear angle relative to the secondmagnetization direction. The magnetic memory device also has thirdmagnetic layer having a third magnetization direction. A firstmagnetoresistive layer is interposed between the third magnetic layerand the second magnetic layer. A driver circuit is connected to one ormore of the layers of the magnetic device to apply driver current to themagnetic device to create a signal based at least in part on an angularrelationship between the third magnetization direction and the secondmagnetization direction. An X direction is orthogonal to the Z directionand a Y direction is orthogonal to the X direction and to the Zdirection. The method also includes applying an external field to theoscillator device, measuring the signal, associating a measurement ofthe signal with the presence of the external field.

Another aspect of the invention provides a method of storing informationon a magnetic memory device. The method includes providing a magneticdevice. The magnetic device has a first magnetic layer having a firstmagnetization direction and a second magnetic layer having a secondmagnetization direction. The second magnetic layer is spaced apart fromthe first magnetic layer in the Z direction. A first coupling layer isinterposed between the first and second magnetic layers. The firstmagnetic layer is non-collinearly coupled to the second magnetic layerby the first coupling layer such that, in the absence of externalmagnetic field, the first magnetization direction is oriented at a firstnon-collinear angle relative to the second magnetization direction. Themagnetic memory device also has third magnetic layer having a thirdmagnetization direction. A first magnetoresistive layer is interposedbetween the third magnetic layer and the second magnetic layer. Acircuit is connected to one or more of the layers of the magnetic deviceby at least a pair of leads. The circuit is configured to determine achange in resistance between the pair of leads wherein the change inresistance is based at least in part on the change in the angularrelationship between the third magnetization direction and the secondmagnetization direction caused by a current passing through at least aportion of the device. An X direction is orthogonal to the Z directionand a Y direction is orthogonal to the X direction and to the Zdirection. The method also includes applying a current through at leasta portion of the device to change the angular relationship between thethird magnetization direction and the second magnetization direction,measuring the resistance of the magnetic device to determine the angularrelationship between the third magnetization direction and the secondmagnetization direction and associating a measured relationship betweenthe third magnetization direction and the second magnetization directionwith a value of a bit of information.

Another aspect of the invention provides a method of sensing an externalfield with a magnetic sensor device. The method includes providing amagnetic device, the magnetic device a first magnetic layer having afirst magnetization direction and a second magnetic layer having asecond magnetization direction. The second magnetic layer is spacedapart from the first magnetic layer in the Z direction. A first couplinglayer is interposed between the first and second magnetic layers. Thefirst magnetic layer is non-collinearly coupled to the second magneticlayer by the first coupling layer such that, in the absence of externalmagnetic field, the first magnetization direction is oriented at a firstnon-collinear angle relative to the second magnetization direction. Themagnetic memory device also has third magnetic layer having a thirdmagnetization direction. A first magnetoresistive layer is interposedbetween the third magnetic layer and the second magnetic layer. Acircuit is connected to one or more of the layers of the magnetic deviceby at least a pair of leads. The circuit is configured to determine achange in resistance between the pair of leads, wherein the change inresistance is based at least in part on the change in the angularrelationship between the third magnetization direction and the secondmagnetization direction caused by the application of the externalmagnetic field. An X direction is orthogonal to the Z direction and a Ydirection is orthogonal to the X direction and to the Z direction. Themethod also includes applying an external field to the magnetic device,measuring the resistance of the magnetic device to determine the angularrelationship between the third magnetization direction and the secondmagnetization direction, and associating a measured relationship betweenthe third magnetization direction and the second magnetization directionwith the presence of the external field.

Another aspect of the invention provides a method of creating analternating current output signal from a direct current input signal.The method includes providing a magnetic device having a first magneticlayer having a first magnetization direction and a second magnetic layerhaving a second magnetization direction. The second magnetic layer isspaced apart from the first magnetic layer in the Z direction. A firstcoupling layer is interposed between the first and second magneticlayers. The first magnetic layer is non-collinearly coupled to thesecond magnetic layer by the first coupling layer such that, in theabsence of external magnetic field, the first magnetization direction isoriented at a first non-collinear angle relative to the secondmagnetization direction. The magnetic memory device also has thirdmagnetic layer having a third magnetization direction. A firstmagnetoresistive layer is interposed between the third magnetic layerand the second magnetic layer. A driver circuit is connected to one ormore of the layers of the magnetic device to apply driver current to themagnetic device to create a signal based at least in part on an angularrelationship between the third magnetization direction and the secondmagnetization direction. An X direction is orthogonal to the Z directionand a Y direction is orthogonal to the X direction and to the Zdirection. The method also includes applying a direct current inputsignal through one or more layers of the magnetic device to continuouslychange the angular relationship between the third magnetizationdirection and the second magnetization direction, and receiving analternating current output signal based at least in part on thecontinuous change of the angular relationship between the thirdmagnetization direction and the second magnetization direction.

Another aspect of the invention provides a method of creating a directcurrent output signal from an alternating current input signal. Themethod includes providing a magnetic device having a first magneticlayer having a first magnetization direction and a second magnetic layerhaving a second magnetization direction. The second magnetic layer isspaced apart from the first magnetic layer in the Z direction. A firstcoupling layer is interposed between the first and second magneticlayers. The first magnetic layer is non-collinearly coupled to thesecond magnetic layer by the first coupling layer such that, in theabsence of external magnetic field, the first magnetization direction isoriented at a first non-collinear angle relative to the secondmagnetization direction. The magnetic memory device also has thirdmagnetic layer having a third magnetization direction. A firstmagnetoresistive layer is interposed between the third magnetic layerand the second magnetic layer. A driver circuit is connected to one ormore of the layers of the magnetic device to apply driver current to themagnetic device to create a signal based at least in part on an angularrelationship between the third magnetization direction and the secondmagnetization direction. An X direction is orthogonal to the Z directionand a Y direction is orthogonal to the X direction and to the Zdirection. The method includes applying an alternating current inputsignal through one or more layers of the magnetic device to continuouslychange the angular relationship between the third magnetizationdirection and the second magnetization direction and receiving a directcurrent output signal based at least in part on the continuous change ofthe angular relationship between the third magnetization direction andthe second magnetization direction.

Another aspect of the invention provides a magnetic structure having afirst magnetic layer having a first magnetization direction, a secondmagnetic layer having a second magnetization direction and a couplinglayer interposed between the first and second magnetic layers. Thecoupling layer may comprise at least one non-magnetic element selectedfrom the group consisting of: Ag, Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta,Ti, Re, Os, Au, Al and Si and at least one magnetic element selectedfrom the group consisting of: Ni, Co, Fe, NiPt, NiPd, CoPt, CoPd, FePt,and FePd. The atomic ratio of the at least one non-magnetic element tothe at least one magnetic element may be (100-x):x, where x is an atomicconcentration parameter which causes, or is selected to cause, the firstmagnetic layer to be non-collinearly coupled to the second magneticlayer such that, in the absence of external magnetic field, the firstmagnetization direction is oriented at a non-collinear angle relative tothe second magnetization direction.

Another aspect of the invention provides a magnetic structure having afirst magnetic layer having a first magnetization direction, a secondmagnetic layer having a second magnetization direction, and a couplinglayer interposed between the first and second magnetic layers. Thecoupling layer may comprise at least one non-magnetic component selectedfrom the group consisting of: Ag, Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta,Ti, Re, Os, Au, Al and Si and at least one magnetic component selectedfrom the group consisting of: Ni, Co, Fe, NiPt, NiPd, CoPt, CoPd, FePt,and FePd. The atomic ratio of the at least one non-magnetic component tothe at least one magnetic component is (100-x):x, where x is an atomicconcentration parameter which causes, or is selected to cause, the firstmagnetic layer to be non-collinearly coupled or non-collinearly,non-orthogonally coupled (i.e. both non-collinearly and non-orthogonallycoupled) to the second magnetic layer such that, in the absence ofexternal magnetic field, the first magnetization direction is orientedat a non-collinear angle relative to the second magnetization direction.

Another aspect of the invention provides a magnetic structure having afirst magnetic layer having a first magnetization direction, a secondmagnetic layer having a second magnetization direction and a couplinglayer interposed between the first and second magnetic layers. Thecoupling layer may comprise: at least one non-magnetic elementcomprising Ru and at least one magnetic element comprising Fe. Theatomic ratio of the at least one non-magnetic element to the at leastone magnetic element is (100-x):x, where x is an atomic concentrationparameter greater than 60 and less than 80 and causes, or is selected tocause, the first magnetic layer to be antiferromagnetically coupled tothe second magnetic layer such that, in the absence of external magneticfield, the first magnetization direction is oriented at anantiferromagnetic angle relative to the second magnetization direction.

Another aspect of the invention provides a method for fabricating amagnetic structure. A coupling layer is layered between a first magneticlayer having a first magnetization direction and a second magnetic layerhaving a second magnetization direction. The coupling layer may compriseat least one non-magnetic element selected from the group consisting of:Ag, Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re, Os, Au, Al and Si, andat least one magnetic element selected from the group consisting of: Ni,Co, and Fe. The atomic ratio of the at least one non-magnetic element tothe at least one magnetic element is (100-x):x. The atomic concentrationparameter, x, is selected such that the first magnetic layer isnon-collinearly coupled to the second magnetic layer, such that, in theabsence of external magnetic field, the first magnetization direction isoriented at a non-collinear angle relative to the second magnetizationdirection.

Another aspect of the invention provides a method for fabricating amagnetic structure. An initial magnetic structure is formed by layeringa coupling layer between a first magnetic layer having a firstmagnetization direction and a second magnetic layer having a secondmagnetization direction. The coupling layer may comprise at least onenon-magnetic element selected from the group consisting of: Ag, Cr, Ru,Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re, Os, Au, Al and Si. The first andsecond magnetic layers may each comprise at least one magnetic elementselected from the group consisting of: Ni, Co, and Fe. The initialmagnetic structure is annealed at a temperature over 100° C. to cause atleast some of the at least one magnetic element of the first and secondmagnetic layers to diffuse into the coupling layer such that an atomicratio of the at least one non-magnetic element to the at least onemagnetic element in the coupling layer is (100-x):x. The initialstructure continues to be annealed until x is such that the firstmagnetic layer is non-collinearly coupled to the second magnetic layersuch that, in the absence of external magnetic field, the firstmagnetization direction is oriented at a non-collinear angle relative tothe second magnetization direction.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference to thedrawings and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are illustrated in referenced figures of thedrawings. It is intended that the embodiments and figures disclosedherein are to be considered illustrative rather than restrictive.

FIG. 1 depicts a plot of the normalized magnetization as a function ofexternal magnetic field H for a magnetic structure having a couplinglayer of Mn interposed between Co magnetic layers before and afterannealing.

FIG. 2A shows a magnetic structure according to a particular embodimentof the invention. FIG. 2B is an exploded view of the layers of the FIG.2A structure.

FIG. 3A schematically depicts a first magnetization direction and anumber of exemplary non-collinearly coupled second magnetizationdirections from among the infinite number of possible non-collinearlycoupled second magnetization directions which could be implemented usingthe FIG. 2A structure.

FIG. 3B schematically depicts first and second non-collinearly coupledmagnetization layers and their respective magnetization directionsaccording to a particular embodiment.

FIG. 4 depicts a plot of the equation (1) coupling energy versus angle φwith a number of different relationships of the magnitudes of thebilinear and biquadratic coupling strength parameters J₁ to J₂.

FIG. 5 depicts a magnetic structure layered on a seed layer according toa particular embodiment.

FIGS. 6A, 6B and 6C (collectively, FIG. 6) depict the steps in methodfor fabricating the FIG. 2A structure according to a particularembodiment.

FIG. 7 schematically depicts how annealing can be used as a process forintroducing components from the magnetic layers of the FIG. 2A structureinto the coupling layer of the FIG. 2A structure.

FIG. 8 depicts a plot of bilinear coupling strength, J₁, as a functionof coupling layer thickness, t_(c), for various magnetic structures.

FIG. 9 depicts a plot of biquadratic coupling strength, J₂, as afunction of coupling layer thickness, t_(c), for various magneticstructures.

FIG. 10 depicts a plot of coupling angle as a function of coupling layerthickness, t_(c), for various magnetic structures.

FIG. 11 depicts a plot of coupling layer thickness, t_(c), as a functionof atomic concentration parameter, x, in a magnetic structure fabricatedwith a coupling layer comprising Ru_(100-x)Co_(x).

FIG. 12A depicts a plot of coupling angle as a function of atomicconcentration parameter, x, in a number of magnetic structuresfabricated with a coupling layer comprising Ru_(100-x)Fe_(x).

FIG. 12B depicts a plot of coupling angle as a function of atomicconcentration parameter, x, in a number of magnetic structuresfabricated with a coupling layer comprising Ru_(100-x)Co_(x).

FIG. 13A depicts a plot of bilinear coupling strength, J₁, as a functionof coupling layer thickness, t_(c), for various magnetic structuresfabricated with a coupling layer comprising Ru and Ni.

FIG. 13B depicts a plot of biquadratic coupling strength, J₂, as afunction of coupling layer thickness, t_(c), for various magneticstructures fabricated with a coupling layer comprising Ru and Ni.

FIG. 13C depicts a plot of coupling angle as a function of couplinglayer thickness, t_(c), for various magnetic structures fabricated witha coupling layer comprising Ru and Ni.

FIG. 14 depicts a plot of the normalized magnetization as a function ofexternal magnetic field H for various magnetic structures fabricatedwith a coupling layer comprising Ru and Fe.

FIG. 15 depicts a plot of bilinear coupling strength, J₁, andbiquadratic coupling strength, J₂, as a function of atomic concentrationparameter, x, in a magnetic structure fabricated with a coupling layercomprising Ru_(100-x)Fe_(x).

FIG. 16 depicts a plot of bilinear coupling strength, J₁, as a functionof coupling layer thickness, t_(c), for various magnetic structuresfabricated with a coupling layer comprising Ru_(100-x)Fe_(x) and onemagnetic structure fabricated with a coupling layer comprising Ru.

FIG. 17 depicts a plot of biquadratic coupling strength, J₂, as afunction of coupling layer thickness, t_(c), for various magneticstructures fabricated with a coupling layer comprising Ru_(100-x)Fe_(x).

FIG. 18 depicts a plot of coupling angle as a function of atomicconcentration parameter, x, for various magnetic structures havingdifferent coupling layers.

FIG. 19 depicts a plot of coupling angle as a function of coupling layerthickness, t_(c), for various magnetic structures fabricated with acoupling layer comprising Ru_(100-x)Fe_(x).

FIG. 20 depicts a plot of saturation field as a function of couplinglayer thickness, t_(c), for various magnetic structures fabricated witha coupling layer comprising Ru_(100-x)Fe_(x) or a coupling layercomprising fabricated with a coupling layer comprising Ru_(100-x)Co_(x).

FIG. 21 depicts a plot of coupling angle as a function of atomicconcentration parameter, x, for various magnetic structures havingdifferent coupling layers.

FIG. 22 depicts a plot of coupling angle as a function of coupling layerthickness, t_(c), for various magnetic structures having differentcoupling layers.

FIG. 23 depicts a plot of coupling angle as a function of atomicconcentration parameter, x, for various magnetic structures havingdifferent coupling layers.

FIG. 24 depicts a plot bilinear coupling strength, J₁, as a function ofatomic concentration parameter, x, for various magnetic structuresfabricated with coupling layers comprising Ru, Fe and Mn.

FIG. 25 depicts a plot biquadratic coupling strength, J₂, as a functionof atomic concentration parameter, x, for various magnetic structuresfabricated with coupling layers comprising Ru, Fe and Mn.

FIG. 26 depicts a plot of saturation field as a function of atomicconcentration parameter, x, for various magnetic structures fabricatedwith coupling layers comprising Ru, Fe and Mn.

FIG. 27A schematically depicts a magnetic device according to aparticular embodiment of the invention.

FIG. 27B depicts a plot of coupling angle as a function of temperaturefor a temperature sensor according to a particular embodiment of theinvention.

FIG. 28 schematically depicts a magnetic device according a particularembodiment of the invention.

FIG. 29 schematically depicts a magnetic device according anotherparticular embodiment of the invention.

FIGS. 30A, 30B and 30C schematically depict magnetic devices accordingto particular embodiments of the invention.

FIGS. 31A and 31B schematically depict a magnetic device combined with amemory device according to a particular embodiment of the invention in afirst state and in a second state, respectively.

FIGS. 32A and 32B schematically depict magnetic devices according toparticular embodiments of the invention.

FIGS. 33A and 33B schematically depict magnetic devices according toparticular embodiments of the invention.

FIGS. 34A and 34B schematically depict magnetic devices according toparticular embodiments of the invention.

FIGS. 35A and 35B schematically depict magnetic devices according toparticular embodiments of the invention.

FIGS. 36A and 36B schematically depict magnetic devices according toparticular embodiments of the invention.

FIGS. 37A and 37B schematically depict magnetic devices according toparticular embodiments of the invention.

FIGS. 38A, 38B, 38C and 38D schematically depict magnetic devicesaccording to particular embodiments of the invention.

FIGS. 39A, 39B and 39C schematically depict magnetic devices accordingto particular embodiments of the invention.

FIGS. 40A, 40B, 40C and 40D depict schematic diagrams of circuits formagnetic devices according to particular embodiments of the invention.

FIGS. 41A to 41G schematically depict constructive interference in amagnetic device according to particular embodiments of the invention.

DESCRIPTION

Throughout the following description specific details are set forth inorder to provide a more thorough understanding to persons skilled in theart. However, well known elements may not have been shown or describedin detail to avoid unnecessarily obscuring the disclosure. Accordingly,the description and drawings are to be regarded in an illustrative,rather than a restrictive, sense.

One aspect of the invention provides a structure comprising a couplinglayer for coupling magnetization directions (also referred to asmagnetic moments) of two or more spaced apart magnetic layers. Otheraspects of the invention provide a device comprising two spaced apartmagnetic layers and an interleaving coupling layer, wherein themagnetization directions of the magnetic layers are coupled to oneanother. Other aspects of the invention provide methods for fabricatingsuch structures and devices and/or methods for using such structures anddevices.

Various forms of coupling between the spaced apart magnetic layers maybe possible. Magnetization directions of magnetic layers may beferromagnetically coupled such that, in the absence of an externallyapplied magnetic field, the magnetization directions (or magneticmoments) of the magnetic layers are aligned at (or substantially near)0° with respect to one another. Magnetization directions of magneticlayers may be antiferromagnetically coupled such that, in the absence ofan externally applied magnetic field, the magnetization directions (ormagnetic moments) are aligned at (or substantially near) 180° withrespect to one another. In some embodiments, when the angle between themagnetization directions of spaced magnetic layers is said to besubstantially near a reference angle (e.g. 0° or 90° or 180°), thensubstantially near may be understood to be ±5° from the reference angle.In some embodiments, substantially near may be ±2° from the referenceangle. In some embodiments, substantially near may be ±1° from thereference angle. Magnetization directions of magnetic layers may becoupled such that, in the absence of an externally applied magneticfield, the magnetization directions (or magnetic moments) are aligned ata non-collinear angle φ with respect to one another. For example,non-collinear angles φ may be greater than 0° and less than 180°,greater than 2° and less than 178°, greater than 5° and less than 175°or greater than 10° and less than 170°. Magnetization directions ofmagnetic layers may be coupled such that, in the absence of anexternally applied magnetic field, the magnetization directions (ormagnetic moments) are aligned at a non-orthogonal, non-collinear angle φwith respect to one another. For example, non-collinear angles φ may be:greater than 0° and less than 90° or greater than 90° and less than180°; greater than 2° and less than 88° or greater than 92° and lessthan 178°; greater than 5° and less than 85° or greater than 95° andless than 175°; or greater than 10° and less than 80° or greater than100° and less than 170°.

When discussing magnetization directions herein and arrows depicted inthe drawings that represent magnetization directions discussed herein,it should be understood that such magnetization directions may refer tothe direction of the predominant magnetization direction or the averagemagnetic moment direction of the respective magnetic layer. Themagnetization direction in different regions throughout each magneticlayer may, in reality, deviate from this predominant or averagemagnetization direction. For each magnetic layer, the degree of thisdeviation may depend on the exchange stiffness, A_(ex), of the magneticlayer. The exchange stiffness may account for the direct exchangeinteraction in ferromagnetic materials. If the exchange stiffness,A_(ex), is larger, then the deviation of magnetization around thepredominant or average magnetization direction tends to be smaller,since the direct exchange interaction may cause magnetic moments toalign across the magnetic layer in a predominant magnetizationdirection. In some cases it may be desired that the exchange stiffness,A_(ex), is smaller. This may be achieved by alloying magnetic materialswith elements such as, but not limited to, Ru or Cr. In some cases itmay be desired that the exchange stiffness, A_(ex), in magnetic layersis larger. Many magnetic materials based on Co and Fe, for example, havea relatively large exchange stiffness, A_(ex). In addition to exchangestiffness, fluctuations in local magnetization directions may be causedby or otherwise associated with fluctuations within the magnetic layercaused by impurities, magnetic layer thickness deviations, and magneticlayer anisotropies and demagnetization energies.

FIGS. 2A and 2B depict a magnetic structure 10 comprising a couplinglayer 20 according to one aspect of the invention. Coupling layer 20 ofFIG. 2A is interposed between and in contact with both of a firstmagnetic layer 30 and a second magnetic layer 40, such that first andsecond magnetic layers 30, 40 are spaced apart from one another in the Zdirection (shown in FIGS. 2A and 2B). First magnetic layer 30 has afirst magnetization direction (or magnetic moment) 32 and secondmagnetic layer 40 has a second magnetization direction (or magneticmoment) 42.

First magnetic layer 30 of the illustrated embodiment comprises firstand second first magnetic layer surfaces 36, 38 which comprise opposing,generally planar surfaces 36, 38 that each extend in the X and Ydirections. Any spatial variation of first and second first magneticlayer surfaces 36, 38 in the Z direction (e.g. due to the surfaces notbeing perfectly planar or smooth) may be considerably less (e.g. one ormore orders of magnitude less) than the X and Y extents of firstmagnetic layer surfaces 36, 38. First generally planar first magneticlayer surface 36 may be separated from second generally planar firstmagnetic layer surface 38 by a thickness, t_(m1), in the Z direction. Insome embodiments, thickness, t_(m1), is greater than approximately 0.2nm. In some embodiments, thickness, t_(m1), is greater thanapproximately 0.3 nm. In some embodiments, thickness, t_(m1), is greaterthan approximately 0.5 nm. In some embodiments, thickness, t_(m1), isgreater than approximately 1.0 nm. In some embodiments, thickness,t_(m1), is greater than approximately 1.5 nm. Thickness, t_(m1), is notnecessarily consistent across the entirety of first magnetic layer 30and may vary due to, for example, imperfections in one or both of firstand second first magnetic layer surfaces 36, 38.

Second magnetic layer 40 of the illustrated embodiment comprises firstand second second magnetic layer surfaces 46, 48 which compriseopposing, generally planar surfaces 46, 48 that each extend in the X andY directions. Any spatial variation of first and second first magneticlayer surfaces 46, 48 in the Z direction (e.g. due to the surfaces notbeing perfectly planar or smooth) may be considerably less (e.g. one ormore orders of magnitude less) than the X and Y extents of secondmagnetic layer surfaces 46, 48. First generally planar second magneticlayer surface 46 may be separated from second generally planar secondmagnetic layer surface 48 by a thickness, t_(m2), in the Z direction. Insome embodiments, thickness, t_(m2), is greater than approximately 0.2nm. In some embodiments, thickness, t_(m2), is greater thanapproximately 0.5 nm. In some embodiments, thickness, t_(m2), is greaterthan approximately 1.0 nm. In some embodiments, thickness, t_(m2), isgreater than approximately 1.5 nm. Thickness, t_(m2), is not necessarilyconsistent across the entirety of second magnetic layer 40 and may varydue to, for example, imperfections in one or both of first and secondsecond magnetic layer surfaces 46, 48.

In some embodiments, first and second magnetization directions 32, 42are in planes defined by the X and Y directions. This is not mandatory.One or both of first and second magnetization directions 32, 42 couldextend in any combination of the X, Y and Z directions.

Coupling layer 20 is interposed between first and second magnetic layers30, 40. Coupling layer 20 may comprise first and second coupling layersurfaces 26, 28 which may comprise opposing, generally planar surfaces26, 28 that each extend in the X and Y directions. Any spatial variationof first and second coupling layer surfaces 26, 28 in the Z direction(e.g. due to the surfaces not being perfectly planar or smooth) may beconsiderably less (e.g. one or more orders of magnitude less) than the Xand Y extents of coupling layer surfaces 26, 28. First coupling layersurface 26 may be separated from second coupling layer surface 28 by athickness, t_(c), in the Z direction. In some embodiments, thickness,t_(c), may be between 0.3 nm to 8.0 nm. In some embodiments, thickness,t_(c), may be between 0.3 nm to 2.5 nm. In some embodiments, thickness,t_(c), may be between 0.4 nm to 2.0 nm. In some embodiments, thickness,t_(c), may be between 0.6 nm to 2.0 nm. Thickness, t_(c), is notnecessarily consistent across the entirety of coupling layer 20 and mayvary due to, for example, imperfections in one or both of first andsecond coupling layer surfaces 26, 28.

In some embodiments, first generally planar first magnetic layer surface36 abuts second generally planar coupling layer surface 28 and/or firstgenerally planar coupling layer surface 26 abuts first generally planarsecond magnetic layer surface 46. For example, coupling layer 20 may belayered directly adjacent to first magnetic layer 30 and second magneticlayer 40 may be layered directly adjacent to coupling layer 20. In someembodiments, one or more of first magnetic layer 30, second magneticlayer 40 and coupling layer 20 have different X-Y plane dimensions. Thisis not mandatory. In some embodiments, magnetic layers 30, 40 and/orcoupling layer 20 need not have strictly planar surfaces. Layers 30, 40and/or 20 could conform to the shape of a non-planar substrate. In someembodiments, magnetic layers 30, 40 and/or coupling layer 20 shown inthe views of FIGS. 2A and 2B may represent portions of non-illustratedmagnetic layers and/or a coupling layer which is/are larger than theportions shown in the FIGS. 2A and 2B illustrations.

First magnetic layer 30 may comprise any suitable magnetic layer. Firstmagnetic layer 30 may exhibit a magnetization direction (magneticmoment) 32. For example, first magnetic layer 30 may comprise aferromagnetic material such as, for example, one or more elements oralloys selected from a group consisting of Co, Fe, Ni and alloysthereof. First magnetic layer 30 may additionally or alternativelycomprise Mn (although Mn is not, strictly speaking, ferromagnetic) andalloys thereof. Notably, in elemental form Co, Ni and Fe have aferromagnetic spin arrangement while Mn has antiferromagnetic spinarrangement. First magnetic layer 30 may additionally or alternativelycomprise, for example, one or more elements or alloys selected from agroup consisting of Co, Fe, Ni, and Mn and alloys thereof, and anadditive element, said additive element being one or more elementsselected from a group consisting of B, C, N, O, F, Mg, Al, Si, P, S, Sc,Ti, V, Cr, Mn, Cu, Zn, Ga, Ge, As, Se, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd,Ag, Cd, In, Sn, Sb, Te, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er,Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi and/or alloysthereof. In some embodiments, first magnetic layer 30 additionally oralternatively comprises one of, for example, RuCo, RuFe, RuNi, RuCoFe,RuFeNi, RuCoNi, RuFeCoNi, FeCoB, FeCoNiSiB, FeCoZr, FeCoRu, CoCr, CoCrB,CoPt, FePt, Gd, Dy, MnAs, MnBi, MnSb, MnBiSi, MnBiSiAl, CrO₂, ErO andGdFeCo. In some embodiments, first magnetic layer 30 additionally oralternatively comprises an L10 compound such as, for example, acombination of one or more of Co, Fe, Ni and one or more of Pt and Pd,FePtAg, FePtCu, and FePtCuAg, or an L10 compound with an oxide orcarbon. In some embodiments, first magnetic layer 30 additionally oralternatively comprises CoPt. CoRu, CoRh, CoCr with or without an oxide.In some embodiments, first magnetic layer 30 additionally oralternatively comprises one or more Heusler compounds in the form Co₂ab,where a is at least one element from the group consisting of Mn, Fe andCr, and b is at least one element from the group consisting of Si, Geand Al.

In some embodiments, first magnetic layer 30 additionally oralternatively comprises a composite layer made up of a plurality ofindividual sub-layers, wherein each sub-layer may have the same or adifferent composition. For example, first magnetic layer 30 may comprisea first sub-layer of FeCoB and a second sub-layer of CoFe. In someembodiments, some sub-layers are non-magnetic layers. For example, amagnetic layer may comprise alternating magnetic and non-magneticsub-layers. Such a non-magnetic sub-layer could comprise, for example,coupling layer 20. In some embodiments, the material of first magneticlayer 30 is chosen based at least in part on the material of couplinglayer 20. For example, magnetic layer 30 may be chosen to allowinter-diffusion between magnetic layer 30 and coupling layer 20.

Second magnetic layer 40 may comprise any suitable magnetic layer, andmay be fabricated to exhibit any of the properties and/orcharacteristics and/or may comprise the same materials as discussedherein for first magnetic layer 30. Second magnetic layer 40 may have amagnetization direction (magnetic moment) 42. In some embodiments,second magnetic layer 40 is substantially similar to first magneticlayer 30. In other embodiments, second magnetic layer 40 is differentthan first magnetic layer 30. For example, first and second magneticlayers 30, 40 may differ in composition to thereby induce differentstructural and/or magnetic properties such as, but not limited to,structure, saturation magnetization, anisotropy, cure temperature,exchange stiffness, and/or damping. First and second magnetic layers 30,40 may also differ in size and/or shape. For example, t_(m1) may bedifferent than t_(m2) or the X and/or Y dimensions of first magneticlayer 30 may be different from those of coupling layer 20 and/or secondmagnetic layer 40.

Coupling layer 20 may comprise at least one first group element 22 andat least one second group element 24. The second group element 24 may bereferred to herein as a dopant. The first group elements 22 may comprisenon-magnetic elements while the second group elements 24 may comprisemagnetic elements. Consequently, the first group elements 22 may also bereferred to herein as the non-magnetic group elements 22 and the secondgroup elements 24 may be referred to herein as the magnetic groupelements 24. The at least one first (non-magnetic) group element 22 maycomprise or be selected from the group consisting of Ag, Cr, Ru, Mo, Ir,Rh, Cu, V, Nb, W, Ta, Ti, Re, Os, Au, Al and Si. Each element in thisgroup of non-magnetic elements is known to exhibit at least someantiferromagnetic coupling when the element is used alone (purely oralmost purely) as a coupling layer between a pair of magnetic layersand, consequently, the inventors have strong reason to believe that eachof the elements in this group can exhibit strong antiferromagneticcoupling or non-collinear coupling when suitably doped with at least onesecond (magnetic) group element 22 as discussed herein.

In some currently preferred embodiments, the at least one first(non-magnetic) group element may comprise or be selected from thesub-group consisting of Cr, Ru, Rh, Re, Ir. Each of the non-magneticelements in this sub-group is known to exhibit particularly strongantiferromagnetic coupling when the element is used alone (purely oralmost purely) as a coupling layer between a pair of magnetic layersand, consequently, the inventors have strong reason to believe that eachof the elements in this sub-group can exhibit strong antiferromagneticcoupling or non-collinear coupling when suitably doped with at least onesecond (magnetic) group element 22 as discussed herein. In somecurrently preferred embodiments, the at least one first (non-magnetic)group element may comprise or be selected from the further sub-groupconsisting of Ru, Ir, and Rh. As with the previous sub-group, each ofthe non-magnetic elements in this further sub-group is known to exhibiteven greater antiferromagnetic coupling when the element is used alone(purely or almost purely) as a coupling layer between a pair of magneticlayers and, consequently, the inventors have strong reason to believethat each of the elements in this further sub-group can exhibit strongantiferromagnetic coupling or non-collinear coupling when suitably dopedwith at least one second (magnetic) group element 22 as discussedherein.

In some currently preferred embodiments, the at least one first(non-magnetic) group element comprises or consists of Ru.

The at least one second (magnetic) group element 24 may comprise or beselected from the group consisting of ferromagnetic elements Ni, Co andFe. The at least one second (magnetic) group element 24 may additionallyor alternatively comprise or be selected from the group consisting ofmagnetic elements Mn, Ni, Co and Fe. In some embodiments, the at leastone second (magnetic) group element 24 may additionally comprise apolarizable element selected from the group of Pd and Pt. Suchpolarizable elements could, in some embodiments, be substituted for aportion of the second (magnetic) group elements 24. In some embodiments,Pd or Pt may be substituted one atom for every atom of second group(magnetic) element 24 although this is not mandatory. In someembodiments, up to 90% of the second (magnetic) group elements 24 may besubstituted by Pd or Pt or a combination of Pd and Pt. In someembodiments, Mn may be substituted for a portion of second (magnetic)group elements 24. Notably, in elemental form Co, Ni and Fe have aferromagnetic spin arrangement while Mn has antiferromagnetic spinarrangement. Consequently, as used herein Mn may be referred to hereinas a magnetic element, magnetic atom or magnetic material where it issought to include Mn with ferromagnetic elements Co, Ni and Fe, butferromagnetic elements should be considered to exclude Mn.

The atomic concentration ratio of the at least one first (non-magnetic)group element 22 to the at least one second (magnetic) group element 24within coupling layer 20 may be (100-x):x, where x>0. It should beunderstood that the atomic concentration ratio of the at least one first(non-magnetic) group element 22 to the at least one second (magnetic)group element 24 within coupling layer 20 is an aggregate atomicconcentration ratio that accounts for the composition of the entirecoupling layer 20. Coupling layer 20 may be relatively homogenousthroughout, such that the atomic concentration ratio is generallyconsistent throughout coupling layer 20 or coupling layer 20 may includeregions or portions in which the atomic concentration ratio is higher orlower than the aggregate atomic concentration ratio. For example,coupling layer 20 may be fabricated in sub-layers, each sub-layer havingan individual atomic concentration ratio of the at least one first(non-magnetic) group element 22 to the at least one second (magnetic)group element 24 wherein the aggregate of the individual atomicconcentration ratios (over coupling layer 20) is (100-x):x, where x>0.

The at least one first (non-magnetic) group element 22 and the at leastone second (magnetic) group element 24 and/or the atomic concentrationparameter x in the atomic concentration ratio of the at least one first(non-magnetic) group element 22 to the at least one second (magnetic)group element 24 ((100-x):x, where x>0) may be chosen such that firstand second magnetization directions 32, 42 of first and second magneticlayers 30, 40 are coupled at a non-collinear angle φ with respect to oneanother in the absence of an externally applied magnetic field—in whichcase structure 10, its magnetic layers 30, 40 and/or its magnetizationdirections 32, 42 may be said to be non-collinearly coupled. The atleast one first (non-magnetic) group element 22 and the at least onesecond (magnetic) group element 24 and/or the atomic concentrationparameter x in the atomic concentration ratio of the at least one first(non-magnetic) group element 22 to the at least one second (magnetic)group element 24 ((100-x):x, where x>0) may be chosen such that firstand second magnetization directions 32, 42 of first and second magneticlayers 30, 40 are coupled at a non-orthogonal and non-collinear angle φwith respect to one another in the absence of an externally appliedmagnetic field—in which case structure 10, its magnetic layers 30, 40and/or its magnetization directions 32, 42 may be said to benon-orthogonally and non-collinearly coupled. As discussed in furtherdetail herein, the at least one first (non-magnetic) group element 22,the at least one second (magnetic) group element 24 and/or the atomicconcentration parameter x may be chosen such that the biquadraticmagnetic coupling strength J₂ of coupling layer 20 is greater than orequal to half of the absolute value of the bilinear magnetic couplingstrength J₁ of coupling layer 20. In some embodiments, the couplinglayer thickness t_(c) may also be chosen to create non-collinear and/ornon-orthogonal/non-collinear coupling between magnetic layers 30, 40 ofstructure 10.

The at least one first (non-magnetic) group element 22, the at least onesecond (magnetic) group element 24, the thickness of coupling layer 20(t_(c)) and/or the atomic concentration parameter x may be chosen basedat least in part on the composition of first and second magnetic layers30, 40. The at least one first (non-magnetic) group element 22, the atleast one second (magnetic) group element 24, the thickness of couplinglayer 20 (t_(c)) and/or the atomic concentration parameter x may bechosen based at least in part on the thickness of one or both of firstand second magnetic layers 30, 40 (e.g. t_(m1), t_(m2)). The at leastone first (non-magnetic) group element 22, the at least one second(magnetic) group element 24, the thickness of coupling layer 20 (t_(c))and/or the atomic concentration parameter x may be chosen such that thesaturation field of structure 10 is greater than 1,000 Oe, 3,000 Oe,20,000 Oe or 50,000 Oe. Such high saturation field structures may benon-collinearly coupled, non-orthogonally and non-collinearly coupled orantiferromagnetically coupled. The at least one first (non-magnetic)group element 22, the at least one second (magnetic) group element 24,the thickness of coupling layer 20 (t_(c)) and/or the atomicconcentration parameter x may be chosen such that the biquadraticcoupling strength, J₂, of structure 10 is greater than 0.1 mJ/m², 0.2mJ/m², 0.5 mJ/m², 1.0 mJ/m², 1.5 mJ/m², or even 2.0 mJ/m² and J₂ isgreater than half of the absolute value of J₁. Such high couplingstrength structures may be non-collinearly coupled, non-orthogonally andnon-collinearly coupled or antiferromagnetically coupled. The at leastone first (non-magnetic) group element 22, the at least one second(magnetic) group element 24, the thickness of coupling layer 20 (t_(c))and/or the atomic concentration parameter x may be chosen such thatmagnetic structure 10 may withstand annealing at a temperature of 100°C. or higher, 150° C. or higher, or 200° C. or higher withoutundesirably changing the coupling angle of first and second magneticlayers, 30, 40. Such annealable structures may be non-collinearlycoupled, non-orthogonally and non-collinearly coupled orantiferromagnetically coupled. In some embodiments, it may be desirablefor the coupling angle of first and second magnetic layers 30, 40 tochange with annealing and the at least one first (non-magnetic) groupelement 22, the at least one second (magnetic) group element 24, thethickness of coupling layer 20 (t_(c)) and/or the atomic concentrationparameter x may be chosen such that the coupling angle may becontrollably changed as desired by annealing at a temperature of 100° C.or higher, 150° C. or higher or 200° C. or higher.

In some embodiments, coupling layer 20 may comprise at least one firstgroup element 22 and at least two second group elements 24. The firstgroup elements 22 may comprise non-magnetic elements while the secondgroup elements 24 may comprise magnetic elements. The at least one first(non-magnetic) group element 22 may comprise or be selected from thegroup consisting of Ag, Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re,Os, Au, Al and Si. In currently preferred embodiments, the at least onefirst (non-magnetic) group element may comprise or be selected from thegroup consisting of Ru, Ir, Re, Rh, and Cr. In some currently preferredembodiments, the at least one first (non-magnetic) group elementcomprises or consists of Ru. In currently preferred embodiments, the atleast two second (magnetic) group elements comprise Co and Fe.

The atomic concentration ratio of the first magnetic group element (e.g.Co) to the second magnetic group element (e.g. Fe) may be any suitableratio. As the ratio of the first magnetic group element to the secondmagnetic group element increases, coupling layer 20 may behave more likea coupling layer of the nonmagnetic element 24 (e.g. Ru) and the firstmagnetic group element (e.g. Co) while as the ratio of the firstmagnetic group element to the second magnetic group element decreases,coupling layer 20 may behave more like a coupling layer of thenonmagnetic element 24 (e.g. Ru) and the second magnetic group element(e.g. Fe). In other words, in the case of a RuFeCo coupling layer 20, asthe ratio of Co to Fe increases, coupling layer 20 may behave more likea RuCo coupling layer 20 and as the ratio of Co to Fe decreases,coupling layer 20 may behave more like a RuFe coupling layer 20. Theproperties of a coupling layer 20 that comprises at least one firstgroup element 22 and at least two magnetic group elements 24 maytherefore be estimated or predicted by observing the properties of twocoupling layers 20 each having only one of the at least two magneticgroup elements 24 in combination with the at least on first groupelement 22 and based on the ratio of the first magnetic group element tothe second magnetic group element.

In some embodiments, coupling layer 20 may comprise at least two firstgroup elements 22 and at least one second group element 24. The at leasttwo first group elements 22 may comprise Ru and at least one secondnon-magnetic element comprising or selected from the group consistingof: Ag, Cr, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re, Os, Au, Al and Si. Theat least one second group element 24 may comprise at least one magneticelement comprising or selected from the group consisting of: Ni, Co andFe. The atomic ratio of the at least one first non-magnetic element tothe at least one second non-magnetic element to the at least onemagnetic element is (100-x-y):y:x. In some embodiments, y is less than80. In some embodiments, the at least one second non-magnetic element isselected from the group consisting of Ru, Ir, Re, Rh, and Cr.

In some embodiments, the at least one first (non-magnetic) group element22 and the at least one second (magnetic) group element 24 and/or theatomic concentration parameter x in the atomic concentration ratio ofthe at least one first (non-magnetic) group element 22 to the at leastone second (magnetic) group element 24 ((100-x):x, where x>0) may bechosen such that first and second magnetization directions 32, 42 offirst and second magnetic layers 30, 40 are coupled at anantiferromagnetic angle with respect to one another in the absence of anexternally applied magnetic field—in which case structure 10, itsmagnetic layers 30, 40 and/or its magnetization directions 32, 42 may besaid to be antiferromagnetically coupled. For example, antiferromagneticangles may be: greater than 170° and less than 190° or greater than 175°and less than 185°; greater than 178° and less than 182°; greater than179° and less than 181°; greater than 179.5° and less than 180.5°; oreven 180°.

The at least one first (non-magnetic) group element 22, the at least onesecond (magnetic) group element 24, the thickness of coupling layer 20(t_(c)) and/or the atomic concentration parameter x may be chosen basedat least in part on the composition of first and second magnetic layers30, 40. The at least one first (non-magnetic) group element 22, the atleast one second (magnetic) group element 24, the thickness of couplinglayer 20 (t_(c)) and/or the atomic concentration parameter x may bechosen based at least in part on the thickness of one or both of firstand second magnetic layers 30, 40 (e.g. t_(m1), t_(m2)). The at leastone first (non-magnetic) group element 22, the at least one second(magnetic) group element 24, the thickness of coupling layer 20 (t_(c))and/or the atomic concentration parameter x may be chosen such that thesaturation field of structure 10 is greater than 1,000 Oe, 3,000 Oe,20,000 Oe or 50,000 Oe. The at least one first (non-magnetic) groupelement 22, the at least one second (magnetic) group element 24, thethickness of coupling layer 20 (t_(c)) and/or the atomic concentrationparameter x may be chosen such that the bilinear coupling strength, J₁is greater than 0.3 mJ/m², 0.6 mJ/m² 0.8 mJ/m² and/or the biquadraticcoupling strength, J₂, of structure 10 is greater than 0.1 mJ/m², 0.2mJ/m², 0.5 mJ/m², 1.0 mJ/m², 1.5 mJ/m², or even 2.0 mJ/m² and J₂ isgreater less than half of the absolute value of J₁. The at least onefirst (non-magnetic) group element 22, the at least one second(magnetic) group element 24, the thickness of coupling layer 20 (t_(c))and/or the atomic concentration parameter x may be chosen such thatmagnetic structure 10 may withstand annealing at a temperature of 100°C. or higher, 150° C. or higher, or 200° C. or higher withoutundesirably changing the coupling angle of first and second magneticlayers, 30, 40. In some embodiments, it may be desirable for thecoupling angle of first and second magnetic layers 30, 40 to change withannealing and the at least one first (non-magnetic) group element 22,the at least one second (magnetic) group element 24, the thickness ofcoupling layer 20 (t_(c)) and/or the atomic concentration parameter xmay be chosen such that the coupling angle may be controllably changedas desired by annealing at a temperature of 100° C. or higher, 150° C.or higher or 200° C. or higher.

In some currently preferred embodiments, the at least one first(non-magnetic) group element 22 comprises Ru or alloys thereof and theat least one second (magnetic) group element 24 comprises Fe or alloysthereof. In some currently preferred embodiments, the at least one first(non-magnetic) group element 22 comprises one or more of Cr, Ir, Rh andRe or alloys thereof and the at least one second (magnetic) groupelement 24 comprises one or more of Fe, Ni and Co or alloys thereof. Insome embodiments, the at least one first (non-magnetic) element 22comprises Ru and at least one second non-magnetic element selected fromthe group consisting of: Ag, Cr, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re,Os, Au, Al and Si and the at least one magnetic element comprises or isselected from the group consisting of: Ni, Co and Fe. In someembodiments, first and second magnetic layers 30, 40 comprise at leastone of Co, Ni or alloys thereof. In some embodiments, the at least onesecond (magnetic) group element 24 may additionally comprise apolarizable element selected from the group of Pd and Pt. Suchpolarizable elements could, in some embodiments, be substituted for aportion of the second (magnetic) group elements 24. In some embodiments,Pd or Pt may be substituted one atom for every atom of second group(magnetic) element 24 although this is not mandatory. In someembodiments, up to 90% of the second (magnetic) group elements 24 may besubstituted by Pd or Pt or a combination of Pd and Pt. In someembodiments, Mn may be substituted for a portion of second (magnetic)group elements 24.

In general, first and second magnetization directions 32, 42 may pointin any direction in space and may not be limited to any particularplane(s). It follows that for a given first magnetization direction 32,second magnetization direction 42 may point in an infinite number ofdirections while first and second magnetization directions 32, 43 arenon-collinearly coupled to one another. This description may use thesymbol φ to refer to the angle φ between first and second magnetizationdirections 32, 42. FIG. 3A schematically depicts a first magnetizationdirection 32 and a number of exemplary non-collinearly coupled secondmagnetization directions 42 from among the infinite number of possiblenon-collinearly coupled second magnetization directions 42 which couldbe implemented in structure 10. The scenario depicted in FIG. 3A isexpected in the case of a magnetic layer and/or magnetic structurehaving an XY-plane cross-section with similar dimensions in the X and Ydirections (such as in the case of a device having a generally circularcross-section).

In some embodiments, one of the X or Y direction dimensions of amagnetic layer and/or a magnetic structure is elongated (e.g. issubstantially greater than the other direction, such as, for example,1.5 times greater, double, 10 times greater or even more). Where theXY-plane cross-section of a magnetic layer and/or a magnetic structureis elongated in one of the X or the Y directions, the magnetizationdirection of that magnetic layer will tend to remain in or bepractically limited to the XZ-plane or the YZ-plane respectively.Therefore, by employing an elongated XY-plane cross-section, it may bepossible to reduce the number of pinning layers (or otherwise simplifythe pinning mechanism) for achieving a desired orientation of amagnetization direction in such embodiments, compared to embodimentshaving non-elongated X-Y plane cross-sections.

In addition to limiting the magnetization direction of a magnetic layer,elongation of one of the X (or Y) dimensions relative to the other inthe XY-plane may be employed to control movement of a magnetizationdirection and/or the path of a magnetization direction between itsstable states. Elongation in the XY-plane may be employed to achieve adesired time, current, field, and/or energy for switching amagnetization direction between its stable states. For example, if amagnetic layer is elongated in the X direction, rotation of amagnetization direction oriented in the negative X direction to thepositive X direction may require less time, current, applied field,and/or energy than if the magnetic layer is not elongated in the Xdirection.

For example, FIG. 3B depicts a magnetic structure first magnetic layer30 having a first magnetization direction 32 and a second magnetic layer40 having a second magnetization direction 42 where the first and secondmagnetic layers 30, 40 have XY-plane cross-sections that are elongatedin the X direction. As can be seen from FIG. 3B, second magnetizationdirection 42, is limited to extending in the XZ-plane and has no (orminimal) Y direction component. Accordingly, to maintain thenon-collinear coupling angle between first and second magnetizationdirections 32, 42, second magnetization direction 42 is generallyexpected to exist in two possible positions or states, extending in thepositive Z direction and positive X direction or extending in thepositive Z direction and negative X direction, as shown in FIG. 3B. Asused herein, a state of a magnetic layer should be understood to referto a state of the magnetization direction of the magnetic layer, unlessthe context dictates otherwise. Therefore, it may be possible toincrease the probability of a second magnetic layer 40 having a secondmagnetization direction 42, when non-collinearly coupled to a firstmagnetic layer 30 having a first magnetization direction 32, to orientin specific limited directions by tailoring the XY-plane cross sectionof second magnetic layer 40. In particular, by elongating the XY-planecross-section of a magnetic layer and/or a magnetic structure in the Xdirection, the magnetization direction of that magnetic layer will tendto have a magnetization direction with a minimal or even zero Ydirection component.

First magnetization direction 32 may be coupled to second magnetizationdirection 42 due to the presence of coupling layer 20. The strength orenergy of the coupling between magnetic moments 32, 42 of first magneticlayer 30 and second magnetic layer 40 across coupling layer 20 inmagnetic structure 10 may be characterized using a bilinear couplingstrength parameter, J₁ and biquadratic coupling strength parameter, J₂.Magnetic structure 10 can be characterized or modelled by a bilinearcoupling strength term of the form E₁=±J₁n₁·n₂ where J₁ is the bilinearcoupling constant in mJ/m² and n₁ and n₂ are unit vectors alongmagnetization directions 32, 42 in first magnetic layer 30 and secondmagnetic layer 40 respectively. E₁ is related to the angle of couplingbetween first and second magnetization directions 32, 42 as follows:E₁=±J₁ cos(φ), where φ is the angle of coupling between first and secondmagnetization directions 32, 42. Magnetic structure 10 can also becharacterized or modelled by biquadratic coupling strength (biquadraticenergy density) term of the form E₂=±J₂(n₁·n₂)² where J₂ is thebiquadratic coupling constant in mJ/m². E₂ is related to the angle ofcoupling between first and second magnetization directions 32, 42 asfollows: E₂=±J₂ cos²(φ), where φ is the angle of coupling between firstand second magnetization directions 32, 42.

J₁ and J₂ represent parameters of a model which relates the dependenceof total magnetization of structure 10 in the direction of an externallyapplied magnetic field to a strength of the externally applied magneticfield. The J₁ and J₂ parameters of structure 10 may be experimentallyascertained by applying external magnetic field to structure 10,measuring the magnetization and selecting J₁ and J₂ to best fit themodel to the experimental results. The model may assume magnetic moments32, 42 in first magnetic layer 30 and second magnetic layer 40 areparallel to the film plane (i.e. in a direction that is a linearcombination of the X and Y directions shown in FIG. 2A). The model mayfurther assume that both first magnetic layer 30 and second magneticlayer 40 consist of one or more magnetic sublayers interacting throughthe direct exchange interaction as proposed by C. Eyrich et. al.,PHYSICAL REVIEW B, 90, 235408 (2014), which is hereby incorporatedherein by reference.

Without being bound by theory, it is believed that antiferromagnetic,ferromagnetic and non-collinear coupling are dependent on therelationships between bilinear, J₁, biquadratic, J₂, and higher ordercoupling parameters. For example, it is believed that if the bilinearcoupling parameter, J₁, dominates the other coupling parameter (e.g. theabsolute value of J₁ is greater than half of the sum of the absolutevalues of the other coupling parameters) and J₁ is less than zero, theresulting coupling is ferromagnetic. It is also believed that if thebilinear coupling parameter, J₁, dominates the other coupling parameter(e.g. the absolute value of J₁ is greater than half of the sum of theabsolute values of the other coupling parameters) and J₁ is greater thanzero, the resulting coupling is antiferromagnetic. It is furtherbelieved that if the biquadratic coupling parameter, J₂, dominates (e.g.is greater than half of the sum of the other coupling parameters) and J₁is small, the magnetic moments 32, 42 of first magnetic layer 30 andsecond magnetic layer 40 may be aligned at a non-collinear angle φbetween approximately 80° to 100°, in some embodiments, at 90°, or, insome embodiments, substantially near 90°. Further, it is believed that amixture of the bilinear and biquadratic parameters, J₁, J₂, can resultin non-collinear coupling such that the magnetic moments 32, 42 of firstmagnetic layer 30 and second magnetic layer 40 are aligned at anon-collinear angle φ which may, in some embodiments, be greater than 0°and less than 180°, in some embodiments, between 1° and 179°, in someembodiments, between 5° and 175° or, in some embodiments, between 20°and 160°.

Without being bound by theory, it is believed that non-collinearcoupling angle φ is controlled by the bilinear, J₁, and biquadratic, J₂,coupling parameters and that non-collinear coupling angle φ may bedetermined by minimizing the E_(coupling) according to the followingequation:E _(coupling) =J ₁ cos φ+J ₂ cos² φ  (1)The bilinear coupling parameter, J₁, can either be positive or negative,and the biquadratic, J₂, coupling parameter has a positive value. Bothparameters vary in magnitude/strength. FIG. 4 depicts a plot of theequation (1) coupling energy versus angle φ with four differentrelationships of the magnitudes of J₁ to J₂. The thick solid linerepresents the case in which J₁=1, J₂=0, the thin solid line representsthe case in which J₂ is just greater than J₂=½|J₁/, the dotted linerepresents the case in which J₁=0, J₂=1, and the dashed line representsthe case in which J₂=⅔|J₁/.

As can be seen from FIG. 4, for the thick solid line representing J₁=1,J₂=0, the coupling energy minimum is at approximately φ=180° (i.e.antiferromagnetic coupling between magnetization directions 32, 42)because there is no J₂ component which might tend to cause non-collinearcoupling. If J₂ is increased to just greater than half of J₁ (asrepresented by the thin solid line in FIG. 4), non-collinear couplingmay occur with coupling angles approximately or substantially near toφ=140° and φ=220°. However φ=180° coupling (i.e. antiferromagneticcoupling) may still occur at J₂=½|J₁/. J₂=½|J₁/ may therefore be seen asan approximate threshold between antiferromagnetic coupling andnon-collinear coupling. If J₂ is increased past this threshold ofJ₂=½|J₁/ such that J₂>½|J₁/, then non-collinear coupling will occurwhile antiferromagnetic coupling does not.

If J₂ is further increased such that J₂=⅔|J₁/ (as represented by thedashed line in FIG. 4), non-collinear coupling may occur with couplingangles approximately or substantially near to φ=110° and φ=250°. For acoupling layer where J₁=0, J₂=1, as represented by the dotted line inFIG. 4, the non-collinear coupling angle φ is only determined by J₂ andso the energy minima are at substantially near to φ=90° and φ=270°. IfJ₁ is negative (not depicted), the energy minima may occur atapproximately or substantially near to φ=0° and φ=360° and as J₁approaches zero from below zero, the energy minima may move toward φ=90°

In some embodiments, a magnetic structure (such as magnetic structure10) may be fabricated by layering on top of a seed layer (also referredto herein as an underlayer). For example, FIG. 5 depicts a magneticstructure 10′, substantially similar to magnetic structure 10, layeredon a seed layer 50. Seed layer 50 may comprise any suitable seed layer,as is known in the art. In some embodiments, seed layer 50 may compriseat least one element selected from the group comprising or consisting ofB, C, Si, Ge, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd,Ag, Hf, Ta, W, Re, Ir, Pt, and Au. In some embodiments, seed layer 50may comprise a first sub-layer comprising at least one elementcomprising or selected from the group consisting of: B, Si, Ge, Al, Ti,V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re,Ir, Pt, and Au and a second layer comprising at least one elementcomprising or selected from the group consisting of N, and O.

Seed layer 50 may be used in the fabrication of magnetic structure 10′for one or more of the following reasons: to ease fabrication or forprotection of first magnetic layer 30, to set a growth of magnetic layer30 along a preferred crystallographic orientation, to serve as anelectrical contact, to serve as a protective layer, to maximize thesurface anisotropy at the interface between seed layer 50 and firstmagnetic layer 30, and/or to control thermal conductivity.

In some embodiments, a protective layer may be layered on secondmagnetic layer 40. In the FIG. 5 embodiment, protective layer 55 islayered on second magnetic layer 40 to protect second magnetic layer 40from, for example, oxidation, corrosion, physical wear etc. Protectivelayer 55 may serve as an electrical contact or part of an electricalcontact. Protective layer 55 may comprise any suitable material. Forexample, protective layer 55 may comprise at least one elementcomprising or selected from the group consisting of Al, Ti, V, Cr, Mn,Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Ir, Pt, andAu. In some embodiments, protective layer 55 may additionally oralternatively comprise nitrides such Si—N, Ti—N or oxides such as Ti—O,Al—O, Si—O.

But for seed layer 50 and protective layer 55, magnetic layers 30, 40and coupling layer 20 of magnetic structure 10′ may be substantiallysimilar to magnetic structure 10 and may comprise any of the features ofmagnetic structure 10 described herein. Likewise, magnetic structure 10may be fabricated to comprise a seed layer 50 and/or a protective layer55.

Fabrication

Magnetic structure 10 may be fabricated using any suitable technique. Insome embodiments, structure 10 is fabricated by, for example, physicalvapor deposition (e.g. sputtering), atomic layer deposition, or chemicalvapor deposition. In some embodiments, magnetic structure 10 may befabricated using sputtering, whereby particles are ejected from a solidtarget material due to bombardment of the target by energetic particlessuch as gas ions, as is known in the art.

One aspect of the invention provides a method for fabricating a magneticstructure (e.g. magnetic structure 10). FIG. 6A depicts a first step oflayering a first magnetic layer 30 on a seed layer (also referred to asan underlayer or substrate) 50. This first step may be accomplished bysputtering, such as is depicted in FIG. 6A. For example, a target 39 ofthe same material as is desired for first magnetic layer 30 may bebombarded by energized particles (not shown), such that particles 39A oftarget material 39 are deposited on seed layer 50 to create firstmagnetic layer 30. In some embodiments, first magnetic layer 30 maycomprise a plurality of elements deposited from a single target 39 (e.g.where the target 39 may be prefabricated to have the desired constituentelements as is desired for magnetic layer 30) or may comprise aplurality of materials (e.g. elements) deposited from multiple targets39, each target optionally comprising a different material. As particles39A of target material 39 are deposited on seed layer 50, the thickness,t_(m1), of first magnetic layer 30 increases until a desired thickness,t_(m1), is achieved. As can be seen from FIG. 6A, surface 36 of firstmagnetic layer 30 may not be perfectly planar due to the distribution ofparticles 39A.

Once the desired thickness, t_(m1), is achieved, a coupling layer 20 maybe layered on first magnetic layer 30. FIG. 6B depicts a second step oflayering coupling layer 20 on first magnetic layer 30. This second stepmay be accomplished by sputtering. For example, a target 29 of the sameconstituent materials as is desired for coupling layer 20 may bebombarded by energized particles (not shown), such that particles 29A oftarget material 29 are deposited on first magnetic layer 30 to createcoupling layer 20. In some embodiments, coupling layer 20 may comprise aplurality of elements deposited from a single target 29 (e.g. where thetarget 29 may be prefabricated to have the desired constituent elementsfor coupling layer 20). Such constituent elements which may bepre-fabricated into target 29 may comprise the at least one first(non-magnetic) group element 22 and the at least one second (magnetic)group element 24. In some embodiments, coupling layer 20 may befabricated from a plurality of materials (e.g. elements) deposited frommultiple targets 29, each target 29 optionally comprising a differentmaterial. One of such multiple targets 29 may comprise the at least onefirst (non-magnetic) group element 22 and another one of such multipletargets 29 may comprise the at least one second (magnetic) group element24. In such embodiments, the atomic concentration parameter x may becontrolled, for example, by controlling the relative power of theenergized particles that are used to bombard the various targets 29. Asparticles 29A of target material 29 are deposited on first magneticlayer 30, the thickness, t_(c), of coupling layer 20 grows until adesired thickness, t_(c), is achieved. As can be seen from FIG. 6B, theinterface between surface 28 of coupling layer 20 and surface 36 offirst magnetic layer 30 may not be perfectly planar due to thedistribution of particles 29A and 39A. Further, surface 26 of couplinglayer 20 may not be perfectly planar due to the distribution ofparticles 29A.

Once the desired thickness, t_(c), is achieved, a second magnetic layer40 may be layered on coupling layer 20. FIG. 6C depicts a third step oflayering a second magnetic layer 40 on coupling layer 20. This thirdstep may be accomplished by sputtering, such as is depicted in FIG. 6C.For example, a target 49 of the same material as is desired for secondmagnetic layer 40 may be bombarded by energized particles such thatparticles 49A of target material 49 are deposited on coupling layer 20to create second magnetic layer 40. In some embodiments, target 49 isthe same as target 39 and magnetic layers 30, 40 are made of the samematerial. In other embodiments, targets 39 and 49 may comprise differentmaterials such that first and second magnetic layers 30, 40 may comprisedifferent materials. In some embodiments, second magnetic layer 40 maycomprise a plurality of elements deposited from a single target 49 (e.g.where the target 49 may be prefabricated to have the desired constituentelements for magnetic layer 40) or may comprise a plurality of materials(e.g. elements) deposited from multiple targets 49, each target 49optionally comprising a different material. As particles 49A of targetmaterial 49 are deposited on coupling layer 20, the thickness, t_(m2),of second magnetic layer 40 grows until a desired thickness, t_(m2), isachieved. As can be seen from FIG. 6C, the interface between surface 26of coupling layer 20 and surface 46 of second magnetic layer 40 may notbe perfectly planar due to the distribution of particles 29A and 39A.Further, surface 48 of second magnetic layer 40 may not be perfectlyplanar due to the distribution of particles 49A.

In some embodiments, protective layer 55 may be layered on top of secondmagnetic layer 40 to protect the magnetic structure. For example, alayer of Ru may be layered on top of second magnetic layer 40 usingsputtering or any other suitable technique.

In some embodiments, the sputtering process occurs in a single chamberthat contains targets 29, 39, 49. In other embodiments, separatechambers are employed for sputtering one or more of targets 29, 39, 49.

In some embodiments, a coupling layer 20 may be fabricated to comprise acompound made of at least one first (non-magnetic) group element 22 andat least one second (magnetic) group element 24 in whole or in partthrough annealing. For example, a coupling layer 20 comprising a first(non-magnetic) group element 22 may be layered between first and secondmagnetic layers 30, 40, where each of the first and second magneticlayers 30, 40 comprise at least one element from second (magnetic) group24 to form an initial structure. This initial structure may befabricated using, for example, sputtering as explained above inconnection with FIG. 6. The initial structure 10 may then be annealed.During the annealing process, second (magnetic) group element 22 atomsfrom magnetic layers 30, 40 may diffuse from first and second magneticlayers 30, 40 into coupling layer 20, such that the composition ofcoupling layer 20 will change from comprising at least one first(non-magnetic) group element 22 to comprising at least one element offirst (non-magnetic) group 22 and at least one element from second(magnetic) group 24. Similarly, annealing may be employed to modify theconcentration of second (magnetic) group element 24 within a couplinglayer 20 that already comprises elements from both first (non-magnetic)group 22 and second (magnetic) group 24.

FIG. 7 schematically depicts this annealing-based process to fabricate amagnetic structure 10. In the initial structure on the left hand side ofFIG. 7, first and second magnetic layers 30, 40 are fabricated (e.g. bysputtering) from a second (magnetic) group element (e.g. Co) and aninitial coupling layer 20′ is fabricated (e.g. by sputtering) a first(non-magnetic) group (e.g. Ru). Then the initial structure is annealedto provide the resultant structure 10 on the right hand side of FIG. 7.During the annealing process, atoms diffuse across the interfacesbetween magnetic layers 30, 40 and initial coupling layer 20′ to form afinal coupling layer 20 comprising both first (non-magnetic) and second(magnetic) group elements. In addition to magnetic atoms from magneticlayers 30, 40 diffusing into initial coupling layer 20′, somenon-magnetic atoms from initial coupling layer 20′ may diffuse intomagnetic layers 30, 40. Accordingly, final coupling layer 20 may bethicker than initial coupling layer 20′.

In some embodiments, during the annealing process, the initial structurecomprises an initial coupling layer 20′ comprising a first(non-magnetic) group element 22 and a second (magnetic) group element 24in an atomic ratio of (100-y):y. After annealing, final coupling layercomprises an atomic ratio of first group element 22 to second groupelement 24 of (100-x):x. In some embodiments, such as was discussedabove, y is equal to 0. In other embodiments, y is greater than 0. Insome embodiments, y is less than x. The atomic concentration parameter,x, may be greater than y due to diffusion of second group elements 24into coupling layer 20 from magnetic layers 30, 40 as discussed above.Accordingly, annealing may be employed to raise the concentration ofsecond group element 24 in coupling layer 20 during fabrication toobtain a desired atomic concentration ratio of a first group element 22to a second group element 24.

In some embodiments annealing comprises heating at least a portion ofthe magnetic structure to over 50° C. during at least a portion offabrication. In some embodiments annealing comprises heating at least aportion of the magnetic structure to over 100° C. during at least aportion of fabrication. In some embodiments annealing comprises heatingat least a portion of the magnetic structure to over 150° C. during atleast a portion of fabrication. In some embodiments annealing comprisesheating at least a portion of the magnetic structure to over 200° C.during at least a portion of fabrication. In some embodiments annealingcomprises heating at least a portion of the magnetic structure to over300° C. during at least a portion of fabrication.

In some embodiments, magnetic structure 10 is heated during at least aportion of fabrication (e.g. during physical vapor deposition, atomiclayer deposition, or chemical vapor deposition of one or more of firstmagnetic layer 30, coupling layer 20 and second magnetic layer 40.). Insome embodiments, magnetic structure is heated to over 100° C. during atleast a portion of fabrication. In some embodiments, magnetic structureis heated to over 150° C. during at least a portion of fabrication. Insome embodiments, magnetic structure is heated to over 200° C. during atleast a portion of fabrication. In some embodiments, magnetic structureis heated to over 300° C. during at least a portion of fabrication.Heating during fabrication may encourage diffusion between one or moreof first and second magnetic layers 30, 40 and coupling layer 20 and mayhave a similar effect as annealing. Heating may be employed to achieve adesired atomic concentration parameter for coupling layer 20.

Example Embodiments and Experimental Results

In one particular non-limiting embodiment of the invention, hereinafterreferred to as the RuCo Embodiment, coupling layer 20 comprises Ru as afirst (non-magnetic) group element 22 and Co as a second (magnetic)group element, and first and second magnetic layers 30, 40 each compriseCo. Seed layer 50 may comprise Ta and Ru and protective layer 55 maycomprise Ru. First and second magnetic layers 30, 40 may each have athickness of about 2.0 nm. Coupling layer 20 may comprise additionalelements without substantively affecting operation of magnetic structure10. First and second magnetic layers 30, 40 may also comprise additionalelements without substantively affecting operation of magnetic structure10. For illustrative purposes and simplicity, the additional elements inmagnetic layers 30, 40 and coupling layer 20 may be ignored. Couplinglayer 20 may have ratio of atomic concentration of Ru to Co of(100-x):x, where x>0.

For convenience, the RuCo Embodiment coupling layer may be referred toas Ru_(100-x)Co_(x). A similar naming convention may be used herein forother compositions. For example, a coupling layer having a ratio ofatomic concentration of Ru to Fe of (100-x):x, where x>0, may bereferred to as Ru_(100-x)Fe_(x). Also for convenience, the RuCoEmbodiment magnetic structure 10 may be described using the followingshorthand: Co(t_(m1))/Ru_(100-x)Co_(x)(t_(c))/Co(t_(m2)). This shorthandnotation may also be used for other magnetic structures 10, describedherein. For example, Ni(t_(m1))/Ru_(100-x)Fe_(x)(0.75 nm)/Ni(t_(m2))refers to a magnetic structure having first and second magnetic layers30, 40 of Ni and a coupling layer 20 of Ru_(100-x)Fe_(x) having athickness, t_(c), of 0.75 nm.

FIG. 8 is a plot depicting the dependence of bilinear coupling strengthJ₁ between first and second magnetic layers 30, 40 of a number ofexemplary magnetic structures 10 fabricated in accordance with the RuCoEmbodiment as a function of the thickness t_(c) of coupling layer 20 forvarious values of x between 0 and 61.2 (e.g. where the atomicconcentration ratio of Ru to Co is between 100:0 and 38:61.2). As can beseen from FIG. 8, bilinear coupling strength J₁ of these magneticstructures is dependent on the atomic concentration ratio of Co to Ru incoupling layer 20 as well as the thickness, t_(c), of coupling layer 20.

FIG. 9 is a plot depicting the dependence of biquadratic couplingstrength J₂ of the between first and second magnetic layers 30, 40 ofthe same exemplary magnetic structures depicted in FIG. 8 as a functionof the thickness of coupling layer 20 for various values of x between 0and 61.2. As can be seen from FIG. 9, biquadratic coupling strength J₂of the RuCo Embodiment is dependent on the atomic concentration ratio ofCo to Ru in coupling layer 20 as well as the thickness, t_(c), ofcoupling layer 20.

It is known that for a pure (or relatively pure) Ru coupling layer 20(i.e. x=0), antiferromagnetic coupling occurs for values of betweenapproximately 0.4 nm and 1.1 nm. J₁ for a pure (or relatively pure) Rucoupling layer 20 within this antiferromagnetic region may be describedas oscillating since it has two maximum values (e.g. at approximately0.4 and 0.85 nm) and a minimum value (e.g. at approximately 0.6 nm). Incontrast, for x≥36.8, such a minimum does not occur for a thickness oft_(c)=0.6 nm. Instead, J₁ is relatively larger (e.g. two to three timeslarger as compared to when x=0) for Ru_(63.2)Co_(36.8) (open triangle)and Ru_(55.8)Co_(44.2) (open square) coupling layers 20 at t_(c)=0.6 nm.Accordingly, for x≥36.8, a coupling layer 20 having a thickness ofapproximately 0.6 nm may exhibit strong antiferromagnetic coupling, ascompared to a pure Ru coupling layer 20 having a thickness ofapproximately 0.6 nm.

FIG. 8 shows that the slope of bilinear coupling strength, J₁, as ittrends from positive to negative (e.g. the transition fromantiferromagnetic to ferromagnetic coupling) as thickness, t_(c),decreases becomes less dramatic for x≥44.2 in coupling layer 20 (asshown by the gradual smooth curves for x≥44.2 in coupling layer 20). Fora coupling layer of Ru (i.e. x=0) the region over which J₁ is trendingto zero as thickness, t_(c), decreases, (not shown in FIG. 8) is knownto occur between 0.32 and 0.38 nm. As the concentration of Co in Ru isincreased, the region over which J₁ is trends to zero (has a positiveslope in FIG. 8) occurs over a broader range of thicknesses. ForRu_(63.2)Co_(36.8) (e.g. x=36.8, represented by the open triangle) theregion over which J₁ is trending downwardly as thickness, t_(c),decreases (has a positive slope in FIG. 8) occurs between approximately0.4 and 0.5 nm such that the region is approximately 0.1 nm wide. ForRu_(55.8)Co_(44.2) (e.g. x=44.2, represented by the open square) theregion over which J₁ is trending downwardly as thickness, t_(c),decreases (has a positive slope in FIG. 8) occurs between approximately0.4 and 0.55 nm, such that the transition region is approximately 0.15nm wide. For Ru_(49.6)Co_(50.4) (e.g. x=50.4, represented by the opencircle) only a small amount of data has been collected however one cansee from FIG. 8 that the region over which J₁ is trending downwardly asthickness, t_(c), decreases (has a positive slope in FIG. 8) occursbetween approximately 0.4 and 0.7 nm, such that the region isapproximately 0.3 nm wide. As the Co concentration is further increasedthis region dramatically increases. For example, for Ru_(44.7)Co_(55.3)(e.g. x=55.3, represented by the solid triangle) the region over whichJ₁ is trending downwardly as thickness, t_(c), decreases (has a positiveslope in FIG. 8) occurs between approximately 0.45 and 1.0 nm, such thatthe region is approximately 0.55 nm wide. For both Ru_(40.2)Co_(59.8)(e.g. x=59.8, represented by the solid circle), and Ru_(38.8)Co_(61.2)(e.g. x=61.2, represented by the solid square) the region over which J₁is trending downwardly as thickness, t_(c), decreases (has a positiveslope in FIG. 8) occurs between approximately 0.6 and 1.4 nm, such thatthe region is approximately 0.8 nm wide. As the region of t_(c) valuesover which J₁ is trending downwardly as thickness, t_(c), decreases isincreased, the region of t_(c) values for non-collinear coupling alsoincreases and non-collinear coupling is more easily achievable.

As can be seen from FIG. 9, adding Co to Ru may result in an increase ofthe biquadratic coupling strength, J₂ for certain values of thicknesst_(c) of coupling layer 20. For a coupling layer 20 of pure (orrelatively pure) Ru (e.g. x=0, represented by the open diamond) a smallbiquadratic coupling strength, J₂, is observed. For coupling layers 20having x≥36.8, at a certain thickness the biquadratic coupling strength,J₂, is relatively larger than for pure (or relatively pure) Ru (e.g.x=0), as can be seen from FIG. 9. This relative size of the biquadraticcoupling strength, J₂, as compared to J₂ for pure Ru, is shown generallyto increase with x and also to increase with a decrease in t_(c).

For Ru_(63.2)Co_(36.8) (i.e. x=36.8, represented by the open triangle),a dramatic increase in the biquadratic coupling strength, J₂, occurs fort_(c) between approximately 0.45 and 0.5 nm. For Ru_(55.8)Co_(44.2)(i.e. x=44.2, represented by the open square), a dramatic increase inthe biquadratic coupling strength, J₂, occurs for t_(c) betweenapproximately 0.55 and 0.6 nm. For Ru_(44.7)Co_(55.3) (i.e. x=55.3,represented by the solid triangle), a dramatic increase in thebiquadratic coupling strength, J₂, occurs for t_(c) betweenapproximately 0.8 and 0.9 nm. For Ru_(40.2)Co_(59.8) (i.e. x=59.8,represented by the solid circle) the dramatic increase in thebiquadratic coupling strength, J₂, occurs between approximately 1.1 and1.2 nm.

These dramatic increases of the biquadratic coupling strength, J₂,allows for non-collinear coupling, which, as discussed above, occurswhen the biquadratic coupling strength, J₂, is large in comparison tothe bilinear coupling strength, J₁. For example, non-collinear couplingmay occur when J₂≥½|J₁|.

FIG. 10 is a plot depicting the dependence of the coupling angle φbetween first and second magnetic layers 30, 40 in a number of exemplarymagnetic structures fabricated in accordance with the RuCo Embodiment asa function of the thickness t_(c) of coupling layer 20 for variousvalues of x between 0 and 63.6.

As can be seen from FIG. 10, non-collinear coupling can be achieved withx≥36.8 at various values of thickness t_(c) of coupling layer 20.

For x=36.8, non-collinear coupling at an angle of about 140° is observedat a coupling layer 20 thickness t_(c) of approximately 0.4 nm.Referring back to FIG. 9, the biquadratic coupling strength, J₂, forx=36.8 is large for values of thickness t_(c) of coupling layer 20 ofbetween approximately 0.4 nm and 0.45 nm. However, the bilinear couplingstrength, J₁, for x=36.8, as shown in FIG. 8, is sufficiently large att_(c)=0.45 nm that J₂ is still less than half of the absolute value ofJ₁ and non-collinear coupling is observed for t_(c)=0.45 nm. Asthickness t_(c) of coupling layer 20 increases to 0.5 nm, J₂ decreasessignificantly and non-collinear coupling is not observed.

If x is increased to 44.2, non-collinear coupling at non-collinearangles φ is observed at a coupling layer 20 thickness t_(c) of betweenapproximately 0.4 nm and 0.55 nm. If x is increased to 50.4,non-collinear coupling at angles between 100° and 180° is observed at athickness t_(c) of coupling layer 20 of between approximately 0.5 nm and0.65 nm. If x is increased to 55.3, non-collinear coupling at anglesbetween approximately 30° and 180° is observed at a thickness t_(c) ofcoupling layer 20 of between approximately 0.45 nm and 0.9 nm.

As can be seen from FIG. 10, for x=36.8, 44.2, 50.4 and 55.3, the rateof change of the non-collinear coupling angle φ with respect tothickness t_(c) of coupling layer 20 decreases as the concentration ofCo (i.e. x) increases. Accordingly, as x increases, non-collinearcoupling may be achieved over a greater range of thickness, t_(c).Moreover, for x=36.8, 44.2, 50.4 and 55.3, the relationship of thenon-collinear coupling angle φ with respect to thickness t_(c) ofcoupling layer 20 is at least approximately linear above 0.4 nm. Thislinear relationship may be due to the relatively large biquadraticstrength, J₂, for x=36.8, 44.2, 50.4 and 55.3 in combination with thesmooth constantly changing bilinear coupling strength, J₁, for x=36.8,44.2, 50.4 and 55.3 as shown in FIGS. 8 and 9.

If x is increased to 59.8, non-collinear coupling at angles between 0°and 180° is observed at a coupling layer 20 thickness t_(c) of betweenapproximately 0.5 nm and 1.1 nm. However, in contrast to x=36.8, 44.2,50.4 and 55.3, the relationship of the non-collinear coupling angle φwith respect to thickness t_(c) of coupling layer 20 for x=59.8 is notlinear. Instead, the coupling angle is relatively constant (lower slope)in an angular range near 85° to 95° for values of coupling layer 20thickness t_(c) between approximately 0.75 nm to 0.85 nm. Therefore itmay be relatively easier to achieve a coupling angle φ near 85° to 95°.This relatively constant coupling angle φ for values of thickness t_(c)of coupling layer 20 between 0.75 nm to 0.85 nm when x=59.8 may be dueto the large biquadratic coupling strength, J₂, combined with therelatively constant bilinear coupling strength, J₁, occurs for values ofthickness t_(c) of coupling layer 20 between 0.75 nm to 0.85 nm whenx=59.8, as can be seen from FIGS. 8 and 9.

If x is increased to 61.2, non-collinear coupling at angles between 15°and 155° is observed at a coupling layer 20 thickness t_(c) of betweenapproximately 0.6 nm and 1.6 nm. In contrast to x=36.8, 44.2, 50.4, 55.3and 59.8, there is no antiferromagnetic coupling for x=61.2 for valuesof coupling layer 20 thickness t_(c) between approximately 0.6 nm and1.6 nm. For values of coupling layer 20 thickness t_(c) betweenapproximately 00.6 nm and 0.9 nm, the relationship of the non-collinearcoupling angle φ with respect to thickness t_(c) of coupling layer 20for x=61.2 is approximately linear. However, similar to the case ofx=59.8 and due to similar reasons, the coupling angle φ is relativelyconstant (lower slope) in an angular range near 85° to 95° for values ofcoupling layer 20 thickness t_(c) between 0.9 nm to 1.0 nm. The couplingangle φ is also relatively constant near 130° for values of couplinglayer 20 thickness t_(c) between 1.1 nm to 1.2 nm. Therefore it may berelatively easier to achieve a coupling angle φ near 130°. However, thecoupling angle φ decreases from approximately 150° at a coupling layer20 thickness t_(c) of 1.3 nm to approximately 55° at a coupling layer 20thickness t_(c) of 1.6 nm. This decrease of the coupling angle φ may bedue to the weak biquadratic coupling strength, J₂, for such values ofcoupling layer 20 thickness t_(c) at x=61.2.

If x is increased to 63, non-collinear coupling at angles φ between 110°and 140° is observed at a coupling layer 20 thickness t_(c) of betweenapproximately 1.2 nm and 1.8 nm. If x is increased to 63.6,non-collinear coupling at angles φ between 45° and 60° is observed at acoupling layer 20 thickness t_(c) of between approximately 1.0 nm and1.4 nm.

From FIG. 10, it can also be seen that antiferromagnetic couplingbetween first and second magnetic layers 30, 40 of magnetic structuresfabricated in accordance with the RuCo Embodiment can be achieved forvalues of x that are greater than 0 and less than 60. For magneticstructures fabricated according to the RuCo Embodiments, FIG. 10 showsnon-collinear coupling angles for a selection of atomic concentrationparameters x in a range of 36.8≤x≤63.6 and coupling layer thicknesses tcin a range of ˜0.38 nm≤t_(c)≤˜1.8 nm. Those skilled in the art willappreciate, from the experimental data provided in FIGS. 8, 9 and 10that non-collinearly coupled structures could be fabricated withsuitable selection of the parameters x and/or t_(c) within these ranges.

FIG. 11 depicts a plot of coupling layer thickness, t_(c), as a functionof atomic concentration parameter, x, for magnetic structures fabricatedaccording to the RuCo Embodiment. FIG. 11 also shows what values ofatomic concentration parameter x and coupling layer thickness t_(c)cause structures fabricated according to the RuCo Embodiment to exhibitferromagnetic coupling, antiferromagnetic coupling, and non-collinearcoupling. Region B represents antiferromagnetic coupling of first andsecond magnetic layers 30, 40, region C represents non-collinearcoupling of first and second magnetic layers 30, 40 and region D of theFIG. 11 plot represents ferromagnetic coupling of first and secondmagnetic layers 30, 40. Regions A and B are separated by boundary E,regions B and C are separated by boundary F, regions C and D areseparated by boundary G. Line H, which is within region C, represents anon-collinear coupling angle of approximately 90°. Boundary Erepresented ferromagnetic coupling.

For structures of the RuCo Embodiment shown in FIG. 11 and for any ofthe atomic concentration parameter x from about 20-55, the range ofthickness t_(c), over which either antiferromagnetic coupling ornon-collinear coupling occurs (i.e. the range of t_(c) between boundaryE and boundary G) increases with x. Similarly, over this sameconcentration parameter range (20≤x≤55), the range of thickness t_(c),over which non-collinear coupling occurs (i.e. the range of t_(c)between boundary F and boundary G or, equivalently, the range of t_(c)in region C) increases with x. With a larger range of thickness t_(c)over which non-collinear coupling occurs, it becomes easier to fabricatecoupling layers 20 that provide non-collinear coupling, since thetolerances for coupling layer thickness t_(c)are greater. With x belowapproximately 36.8, the range of values of thickness t_(c) of couplinglayer 20 for which non-collinear coupling occurs is relatively smallerthan for x above approximately 36.8. For example, at x=20, non-collinearcoupling may be observed for t_(c) values of greater than approximately0.35 nm and less than approximately 0.4 nm. On the other hand, atx=44.2, non-collinear coupling is observed to occur for t_(c) values ofgreater than approximately 0.35 nm and less than approximately 0.5 nmand at x=55.3, non-collinear coupling is observed to occur for t_(c)values of greater than approximately 0.45 nm and less than approximately0.9 nm.

Non-collinear coupling may occur in structures fabricated according tothe RuCo Embodiment for the following values of x and the correspondingvalues of t_(c):

-   -   for 37<x<44, (0.0014x+0.3)<t_(c)[nm]<(0.017x−0.17);    -   for 44<x<50, (0.0072x+0.064)<t_(c)[nm]<(0.017x−0.18);    -   for 50<x<55, (0.0072x+0.044)<t_(c)[nm]<(0.044x−1.52);    -   for 55<x<60, (0.03x−1.2)<t_(c)[nm]<(0.044x−1.54); and    -   for 60<x<63, (0.14x−7.8)<t_(c)[nm]<(0.07x−2.61).        Below x=37, non-collinear may occur but only for very small        ranges of thickness, t_(c). Experimental results are not        currently available for x is greater than 64. However, it is        expected that non-collinear coupling may occur for some values        of t_(c) when x is greater than 64.

As values of coupling layer thickness t_(c) increase, coupling strengthbetween magnetic layers 30, 40 may weaken due to the increased distancebetween magnetic layers 30, 40.

For fabrication of magnetic structures, like magnetic structure 10, itmay be beneficial for structural reliability, ease of manufacturingand/or consistency of manufacturing, if the range of t_(c) values at agiven value of x for which non-collinear coupling occurs is relativelylarger. Similarly, it may be beneficial for ease of manufacturing and/orconsistency of manufacturing, if the range of t_(c)values for which aparticular non-collinear coupling angle φ (or a particular range ofnon-collinear coupling angles φ) occurs is larger. This may allow forreduced manufacturing tolerances while still achieving non-collinearcoupling or non-collinear coupling with a particular coupling angle (orrange of angles) φ.

FIG. 12A is a plot depicting the dependence of coupling angle φ on theatomic concentration parameter, x, for two different thicknesses,t_(m1), t_(m2), of magnetic layers 30, 40, where t_(m1) is approximatelyequal to t_(m2), for a magnetic structure 10 ofCo(t_(m1))/Ru_(100-x)Fe_(x)(0.75 nm)/Co(t_(m2)). From FIG. 12A, it canbe seen that both of the depicted structures exhibit non-collinearcoupling for x≥˜79. However, in general, FIG. 12A shows that thecoupling angle φ is dependent on both atomic concentration parameter, x,and the thicknesses, t_(m1), t_(m2), of magnetic layers 30, 40, wheret_(m1) is approximately equal to t_(m2). It can also be seen from FIG.12A that, in the case of a magnetic structure 10 ofCo(t_(m1))/Ru_(100-x)Fe_(x)(0.75 nm)/Co(t_(m2)), non-collinear couplingoccurs over a wider range of values (and at lower values) of atomicconcentration parameter, x, for lower values of thicknesses, t_(m1),t_(m2) and the rate of change of the coupling angle φ with respect tothe parameter x is greater for larger values of thicknesses, t_(m1),t_(m2). FIG. 12A shows that independent of magnetic layer thickness,t_(m1), t_(m2), orthogonal or near orthogonal non-collinear coupling mayoccur at relatively similar values of the atomic concentrationparameter, x. However, the rate of change of coupling angle φ withrespect to atomic concentration parameter, x, when orthogonal or nearorthogonal non-collinear coupling occurs may be different, as can beseen by the varying steepness of the curves in FIG. 12A as the curvescross the orthogonal (φ=90°) non-collinear coupling line. While FIG. 12Ashows that the dependence of coupling angle φ on the atomicconcentration parameter, x, is different for t_(m1) and t_(m2) equal to2 nm or 8 nm, it is expected that less substantial differences in t_(m1)and t_(m2) would have less substantial impacts on the dependence ofcoupling angle φ on the atomic concentration parameter, x. For example,it is expected that if t_(m1) and t_(m2) are greater than 1.5 nm andless than 3 nm, the dependence of coupling angle φ on the atomicconcentration parameter, x, would be relatively similar (e.g. within10%, 5% or 2%).

FIG. 12B is a plot depicting the dependence of coupling angle φ on theatomic concentration parameter, x, for three different values ofcoupling layer 20 thickness, t_(c) for a magnetic structure ofCo(t_(m1))/Ru_(100-x)Co_(x)(t_(c))/Co(t_(m2)). From FIG. 12B, it can beseen that the coupling angle φ is dependent on both atomic concentrationparameter, x, and the thickness, t_(c), of coupling layer 20. It canalso be seen that non-collinear coupling occurs for lower values ofatomic concentration parameter, x, when coupling layer 20 is thinner(i.e. for lower values of t_(c)) and the rate of change of the couplingangle φ with respect to the atomic concentration parameter x in thenon-collinear coupling region is greater for larger values of couplinglayer thickness, t_(c). Non-collinear coupling may occur for lowervalues of atomic concentration parameter, x, when coupling layer 20 isthinner (i.e. for lower values of t_(c)) due to the relatively largerimpact (at small t_(c) values) for diffusion of magnetic material frommagnetic layers 30, 40 into coupling layer 20.

FIGS. 13A and 13B are plots depicting the dependence of bilinearcoupling strength J₁ and biquadratic coupling strength J₂, respectively,of the magnetic coupling between first and second magnetic layers 30, 40as a function of the thickness t_(c) of coupling layer 20 for magneticstructure 10 of Co(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2)). FIG. 13Cshows a dependence of the coupling angle φ of first and secondmagnetization directions 32, 42 on the thickness, t_(c) for a magneticstructure 10 of Co(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2)). Theseplots of FIGS. 13A, 13B and 13C are similar to the plots of FIGS. 8, 9and 10 for magnetic structures 10 fabricated according to the RuCoEmbodiment.

For atomic concentration parameter, x, of 51, bilinear coupling strengthJ₁ is negative and bilinear coupling strength J₁ increases steeply forlow values of coupling layer 20 thickness t_(c). As bilinear couplingstrength J₁ crosses to positive values, J₁ remains relatively constantas t_(c) values increase from about 0.58 nm to about 1.1 nm. Biquadraticcoupling strength, J₂, for magnetic structure 10 ofCo(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2)) atomic concentrationparameter, x, of 51 is at a maximum when coupling layer 20 thickness,t_(c), is approximately 0.5 nm and biquadratic coupling strength, J₂,decreases as coupling layer 20 thickness, t_(c), increases.

FIG. 13C shows a dependence of the coupling angle φ of first and secondmagnetization directions 32, 42 on the thickness, t_(c) for a pair ofmagnetic structures 10 of Co(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2))having different values for the atomic concentration parameter x. As canbe seen from FIG. 13C, non-collinear coupling may be achieved formagnetic structure 10 of Co(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2))when thickness, t_(c), is greater than approximately 0.5 nm and lessthan about 0.8 nm for x=51 and greater than approximately 0.7 and lessthan about 0.85 nm for x=57. When thickness, t_(c), is above 0.85 nm,magnetic structure 10 of Co(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2))exhibits antiferromagnetic coupling between first and second magneticlayers 30, 40 for 51≤x≤57. The results exhibited in FIGS. 13A, 13B, 13Cfor magnetic structures 10 ofCo(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2)) are similar to those shownin the plots of FIGS. 8, 9 and 10 for magnetic structures 10 fabricatedaccording to the RuCo Embodiment. Accordingly, although there arelimited experimental results for theCo(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2)) embodiment, those skilledin the art could, based on the experimental data shown, select theparameters x and/or t_(c) to achieve magnetic structures ofCo(t_(m1))/Ru_(100-x)Ni_(x)(t_(c))/Co(t_(m2)) exhibiting non-collinearcoupling.

FIG. 14 shows the normalized magnetization as a function of externalmagnetic field H for a number of magnetic structures 10 of Co(2.0nm)/Ru_(100-x)Fe_(x)(0.75 nm)/Co(2.0 nm) with different x values, where49≤x≤68.5. The saturation field as discussed herein is defined as thesmallest external magnetic field required to fully saturate first andsecond magnetic layers 30, 40, along the applied field direction (e.g.to align magnetic moments 32, 42 along the applied external fielddirection). At or above the saturation field, the normalizedmagnetization M/Ms is equal to 1. M is the measured magnetization at thegiven external magnetic field H and Ms is the saturation magnetization.In FIG. 14, the vertical solid lines are used to identify the saturationfields for magnetic structure 10 for each value of x (e.g. for each ofx=49, 55.4, 61 and 68.5).

As can be seen from FIG. 14, the saturation field in the FIG. 14structures significantly increases if Fe concentration, x, is above 60.The saturation field for antiferromagnetic coupling increases as J₁ andJ₂ increase, such that J₂≤½J₁. Accordingly, the increase in saturationfield shown in FIG. 14 is due to the increase in bilinear couplingstrength J₁ when x is above 60 and the large values of J₂ that occurwhen x is above 60. J₂ is seen to be substantially smaller for x is lessthan 60 which leads to smaller saturation fields for x is below 60. Theantiferromagnetic coupling strength is expected to increase forstructures having a Ru_(100-x)Fe_(x) coupling layer for magnetic layers30, 40 having a wide range of materials (e.g. other than pure Co), if xis above 60 and x is below values where non-collinear coupling isobserved.

FIG. 15 is a plot of J₁ and J₂ for a magnetic structure 10 ofNi(t_(m1))/Ru_(100-x)Fe_(x)(0.75 nm)/Ni(t_(m2)) as a function of x. Formagnetic structure 10 of Ni(t_(m1))/Ru_(100-x)Fe_(x)(0.75nm)/Ni(t_(m2)), antiferromagnetic coupling between Ni magnetic layers isachieved for values of x greater than approximately 60 and less thanapproximately 74. Antiferromagnetic coupling between Ni magnetic layers30, 40 quickly diminishes (both J₁ and J₂ are around zero) if x is below60.

If a magnetic structure 10 has the structureCo(t_(m1))/Ru(t_(c))/Co(t_(m2)), the antiferromagnetic coupling strengthbetween Co magnetic layers 30, 40 across a Ru coupling layer 20, forcoupling layer 20 thickness, t_(c), greater than approximately 0.35 nmand less than approximately 1.1 nm, is relatively large (e.g. forCo(t_(m1))/Ru(0.75 nm)/Co(t_(m2)), the bilinear coupling strength J₁ isapproximately 0.65 mJ/m² and the biquadratic coupling strength, J₂ isapproximately near zero). In contrast, if magnetic structure 10 has thestructure Ni(t_(m1))/Ru(t_(c))/Ni(t_(m2)), the antiferromagneticcoupling strength and saturation field between Ni magnetic layers 30, 40across a Ru coupling layer 20 is weak (e.g. at or near zero). However,if magnetic structure 10 has the structure,Ni(t_(m1))/Ru_(100-x)Fe_(x)(t_(c))/Ni(t_(m2)), where x is greater thanapproximately 60 and less than approximately 74, the antiferromagneticcoupling strength between first and second magnetic layers 30, 40 andsaturation field are comparable to that of a magnetic structure 10having the structure Co(t_(m1))/Ru(t_(c))/Co(t_(m2)). This can be seenin FIG. 15, where the magnitudes of both J₁ and J₂ increase from x=60 tox=74 for Ni(t_(m1))/Ru(0.75)/Ni(t_(m2))

For a structure 10 of Ni(t_(m1))/Ru_(29.5)Fe_(70.5)(0.75 nm)/Ni(t_(m2))as shown in FIG. 15, the antiferromagnetic coupling strength andsaturation field are comparable to that of a Co(t_(m1))/Ru(0.75nm)/Co(t_(m2)). Antiferromagnetic coupling may also occur between firstand second magnetic layers 30, 40 of Ni in a magnetic structure ofNi(t_(m1))/Ru_(22.2)Fe_(77.8)(1.6 nm)/Ni(t_(m2)). There are manystructures in which it may be preferable for first and second magneticlayers 30, 40 to comprise Ni. Previously, the antiferromagnetic couplingbetween Ni magnetic layers was achieved by separating Ni magnetic layersusing a film having a first layer of Co (or Fe, or a Co or Fe alloy), asecond layer of Ru and a third layer of Co (or Fe, or a Co or Fe alloy).By employing Ru_(100-x)Fe_(x) coupling layers 20, the addition of Cointerface layers can be avoided.

There is large price difference between Fe and Ru. Ru is a member of theplatinum group, making it an expensive material. Accordingly, otherthings being equal, a coupling layer 20 comprising a relatively high Feconcentration and relatively low concentration of Ru (as compared to arelatively low (or no) concentration of Fe and a relatively highconcentration of Ru) is ideal for commercial applications as the priceof the material used for the coupling layer is dramatically reduced.

FIGS. 16 and 17 respectively show J₁ and J₂ for a number of magneticstructures 10 of Co(2.0 nm)/Ru_(100-x)Fe_(x)(t_(c))/Co(2.0 nm) where x=0(not shown in FIG. 17), 22.6, 70.55, 72.15, 75, 77.8 and 79 and wheret_(c) is greater than 0.4 and less than 1.35 nm. FIG. 16 shows that J₁is the largest for x=0 and 22.6 and t_(c) between 0.4 and 0.5 nm. Forx=70.55, 72.15 and 75, J₁ decreases with increasing t_(c). For t_(c)greater than 0.55 and less than 0.75 nm, J₁ for x=70.55, 72.15, and 75is larger than J₁ for x=0 and 22.6. For x=77.8, J₁ is practically zerofor t_(c) between 0.45 and 1.3 nm in Co(2.0nm)/Ru_(100-x)Fe_(x)(t_(c))/Co(2.0 nm). For x=79, J₁ is a negative valuefor t_(c) greater than 0.55 and less than 1.35 nm in Co(2.0nm)/Ru_(100-x)Fe_(x)(t_(c))/Co(2.0 nm). FIG. 16 therefore showsdependence of J₁ on x.

FIG. 17 shows that J₂ increases with increasing x. For x=22.6, J₂ ispractically zero for t_(c) greater than 0.4 and less than 1.1 nm. Forx=0, 22.6, 70.55, 72.15, 75, 77.8 and 79, J₂ decreases with increasingt_(c) for t_(c) greater than approximately 0.47 and less than 0.9 nm.For x=77.8 and 79, J₂ is relatively large (e.g. comparable in magnitudeto J₁ for a magnetic structure 10 of Co(t_(m1))/Ru(0.4 nm)/Co(t_(m1)).

FIG. 18 depicts a plot of coupling angle φ as a function of the atomicconcentration parameter, x, for various magnetic structures 10 havingdifferent coupling layers 20. In the magnetic structures 10 presented inFIG. 18, the coupling between the magnetic moment 32, 42 of firstmagnetic layer 30 and second magnetic layer 40 changes fromantiferromagnetic to non-collinear to ferromagnetic as x increases. Forlower values of x, the coupling between first and second magnetic layers30, 40 is antiferromagnetic. As x increases further (i.e. the atomicconcentration of Co, Ni, or Fe increases further relative to the atomicconcentration of the first group element 24—Ru or Cr, as the case maybe), the coupling transitions to non-collinear coupling, where the anglebetween the magnetic moments 32, 42 of first magnetic layer 30 andsecond magnetic layer 40 is a non-collinear angle. Further increases ofx leads to ferromagnetic coupling, where the angle between the magneticmoments 32, 42 of first magnetic layer 30 and second magnetic layer 40is 0°.

It may be desirable for the range of x in coupling layer 20, for whichthe coupling between magnetic layers 30, 40 is non-collinear (referredto herein as Δx), to be as large as possible. Increased Δx enablesbetter control of the angle φ between magnetic moments 32, 42 of firstand second magnetic layers 30, 40 in magnetic structure 10. Relativelylarge Δx facilitates fabrication of coupling layer 20 by reducing thenecessity for stringent manufacturing tolerances on x, and distributionof second group element 24 in first group element 22. In someembodiments, Δx may depend on the composition of first and secondmagnetic layers 30, 40 and the composition and/or thickness t_(c) ofcoupling layer 20, since the atoms of first and second magnetic layers30, 40 and of coupling layer 20 may interact with one another (e.g.atoms from first and second magnetic layers 30, 40 may diffuse intocoupling layer 20).

Pure (or almost pure) Ru coupling layers have been employed to establishantiferromagnetic coupling between magnetic layers. One aspect of theinvention provides that by adding second group elements 24 (e.g.magnetic atoms) to Ru (e.g. a first group element 22), the angle ofcoupling φ between first magnetic layer 30 and second magnetic layer 40may be controlled as desired. FIG. 18 shows how the angle φ betweenmagnetic moments 32, 42 depends on x, where first and second magneticlayers 30, 40 comprise Co, Fe, Ni, NiFe, CoNi, and CoFeB. From FIG. 18it follows that:

-   -   For a magnetic structure 10 of Ni(t_(m1))/Ru_(100-x)Fe_(x)(0.75        nm)/Ni(t_(m2)), the coupling between first and second magnetic        layers 30, 40 layers is observed to be antiferromagnetic if x is        less than or equal to about 70.5. If x is greater than        approximately 70.5 and less than approximately 89.5 (or even        94), the coupling angle φ between first and second magnetic        layers 30, 40 is non-collinear.    -   For a magnetic structure 10 of Co(t_(m1))/Ru_(100-x)Fe_(x)(0.75        nm)/Co(t_(m2)), the coupling between first and second magnetic        layers 30, 40 is observed to be antiferromagnetic if x is less        than or equal to about 68.2. If x is greater than approximately        68.2 and less than approximately 80.4 (or even 82), the coupling        angle φ between first and second magnetic layers 30, 40 is        non-collinear.    -   For a magnetic structure 10 of Co(t_(m1))/Ru_(100-x)Co_(x)(0.75        nm)/Co(t_(m2)), the coupling between first and second magnetic        layers 30, 40 is observed to be antiferromagnetic if x is less        than or equal to about 50.3. If x is greater than approximately        50.3 and less than approximately 61.2 (or even 64), the coupling        angle φ between first and second magnetic layers 30, 40 is        non-collinear.    -   For a magnetic structure of        Co(t_(m1))/Ru_(100-x)(Co_(100-y)Fe_(y))_(x)(0.55 nm)/Co(t_(m2))        where y=50, the coupling between first and second magnetic        layers 30, 40 is antiferromagnetic if x is less than or equal to        about 59.0. If x is greater than approximately 59.0 and less        than approximately 76.5 (or even 80), the coupling angle φ        between first and second magnetic layers 30, 40 is observed to        be non-collinear. The transition from antiferromagnetic to        ferromagnetic coupling in the structure of        Co(t_(m1))/Ru_(100-x)(Co_(100-y)Fe_(y))_(x)(0.55 nm)/Co(t_(m2))        is observed to occur for a larger atomic concentration parameter        x than for Co/Ru_(100-x)Co_(x)(7.5 A)/Co and at the lower        magnetic atom concentration than for Co/Ru_(100-x)Fe_(x)(7.5        A)/Co as discussed in more detail in relation to FIG. 23.    -   After annealing of a magnetic structure 10 of        Co(t_(m1))/Ru_(100-x)Fe_(x)(0.75 nm)/Co(t_(m2)) at 200° C. (i.e.        represented by solid line with solid diamonds in FIG. 18),        non-collinear coupling is observed over a greater range of        values of x. The occurrence of non-collinear coupling over a        greater range of values of x (including lower values of x prior        to annealing) may be due to the diffusion of magnetic material        from magnetic coupling layers 30, 40 into coupling layer 20. It        can also be seen that the angle φ between the magnetic moments        of the first and second Co layers 30, 40 changes from 140° for        x=60.9, to 57.6° for x=76. The change in the angle φ between        first and second magnetization directions 32, 42 may be due to        inter-diffusion of atoms at the interfaces between first and        second magnetic layers 30, 40 and coupling layer 20.

From FIG. 18, it can be seen that changes in the material composition ofmagnetic layers 30, 40 for coupling layers 20 of RuCo may increase ordecrease the values of x for which non-collinear coupling is observed.It should also be understood that changes in the material composition ofmagnetic layers 30, 40 for coupling layers 20 other than RuCo would havesimilar effects. For example, it is expected that replacing Co magneticlayers 30, 40 with CoNi for a coupling layer 20 of RuFe would decreasethe atomic concentration parameter x values for which non-collinearcoupling would be observed in a manner similar to the way that replacingCo magnetic layers 30, 40 with CoNi for a coupling layer 20 of RuCo isobserved (form the data presented in FIG. 18) to decrease the atomicconcentration parameter x values for which non-collinear coupling isobserved.

FIG. 19 shows a dependence of the coupling angle φ of first and secondmagnetization directions 32, 42 on the thickness, t_(c) for a number ofmagnetic structures 10 of Co(t_(m1))/Ru_(100-x)Fe_(x)(t_(c))/Co(t_(m2))having different values for their atomic concentration parameters x.From FIG. 19, it can be seen that for a given composition (e.g. atomicconcentration parameter x) of the Ru_(100-x)Fe_(x) coupling layer 20,the coupling angle φ is relatively constant over a wide range ofthickness values, t_(c). For example FIG. 19 shows that for a couplinglayer 20 of Ru_(22.2)Fe_(77.8), the coupling angle φ between magneticmoments 32, 42 is approximately 90° for t_(c) greater than 0.47 nm andless than 0.94 nm. For a coupling layer 20 of Ru₂₅Fe₇₅, the couplingangle φ between magnetic moments 32, 42 is relatively constant (e.g.112°≤φ≤120°) for t_(c) greater than 0.5 nm and less than 0.875 nm, andis relatively constant (e.g. 165°≤φ≤175°) for t_(c) greater than 1.0 nmand less than 1.25 nm. For a coupling layer 20 of Ru_(27.85)Fe_(72.15),the coupling angle φ between magnetic moments 32, 42 is relativelyconstant (e.g. 142°≤φ≤152°) for t_(c) greater than 0.55 nm and less than0.82 nm. For a coupling layer 20 of Ru_(29.45)Fe_(70.55), the couplingangle φ between magnetic moments 32, 42 is relatively constant (e.g.158°≤φ≤164°) for t_(c) greater than 0.63 nm and less than 0.81 nm. FromFIG. 19, it may be understood that in order to obtain a desired couplingangle φ between magnetic moments 32, 42 in a magnetic structure ofCo(t_(m1))/Ru_(100-x)Fe_(x)(t_(c))/Co(t_(m2)), it is relatively moreimportant to precisely control the composition of the Ru_(100-x)Fe_(x)coupling layer 20 (e.g. the atomic concentration parameter x) than toprecisely control the coupling layer 20 thickness, t_(c). Although FIG.19 only shows data for values of x of 70.55, 72.15, 75, 77.8, and 79, itshould be understood that values between 70.55 and 79 could beextrapolated from the FIG. 19 data. For example, it should be expectedthat a line representing x of 71 would fit between the data for x of70.55 and 72.15. It should also be understood that the data presented inFIG. 19 could be extrapolated to t_(c) of 0.4 nm.

FIG. 20 shows the saturation fields for a number of magnetic structures10 of Co(2 nm)/Ru_(100-x)Co_(x)(t_(c))/Co(2 nm) and of Co(2nm)/Ru_(22.2)Fe_(77.8)(t_(c))/Co(2 nm) as a function of t_(c). For acoupling layer 20 of Ru_(56.8)Co_(44.2) with t_(c) of greater than 0.4nm and less than 0.55 nm, the saturation field is relatively constant.For a coupling layer 20 of Ru_(44.7)Co_(55.3) with a t_(c) of greaterthan 0.55 nm and less than 0.9 nm, the saturation field is relativelyconstant. For coupling layers 20 of Ru_(100-x)Co_(x) where x is greaterthan 59.8 and less than 61.2 and t_(c) is greater than 0.7 nm and lessthan 1.2 nm, the saturation field is relatively constant. The saturationfield for a coupling layer 20 of Ru_(22.2)Fe_(77.8) is relativelyconstant when t_(c) is greater than approximately 0.9 nm and less thanapproximately 1.3 nm. Such values of t_(c) across which the saturationfield is relatively constant may facilitate fabrication at relativelylow cost and relatively high reliability (when compared to structureshaving lower values of t_(c) across which the saturation field isrelatively constant) and may thereby improve predictability andreliability of fabrication techniques and the resultant magneticstructures 10. For a coupling layer 20 of Ru_(1-x)Fe_(x) at x=77.8 (andother values not shown), it is possible to achieve a substantiallyhigher saturation field than for a coupling layer 20 of Ru_(1-x)Co_(x)(as can be seen in FIG. 20 for t_(c) of approximately 0.45 nm.

For a magnetic structure of Co(t_(m1))/Ru(t_(c))/Co(t_(m2)), there maybe intermixture or inter-diffusion of Co and Ru at the Co—Ru interfaces.Given that a Ru coupling layer 20 may only be a few monolayers inthickness (e.g. from less than 2 to about 10 monolayers), the Coconcentration may be larger at the Co—Ru interfaces (e.g. the interfacesbetween coupling layer 20 and first and second magnetic layers 30, 40)and smaller near the center of the Ru coupling layer 20. When pure (oralmost pure) Ru layers are less than about 5 monolayers thick, it may beobserved that Co is present through the entire Ru coupling layer 20.Nonetheless, the amount of Co diffusing into Ru is likely to be too lowto cause non-collinear coupling and only antiferromagnetic coupling isobserved.

One aspect of the invention provides that magnetic polarization orpolarizable materials such as Pt and Pd may be substituted for a portionof the at least one second (magnetic) group element 24, such thatcoupling layer 20 comprises at least one element from first groupelements 22, at least one element from second group elements 24 and atleast one polarizable element such as Pt or Pd. This can be seen for thestructure of Co/Ru_(1-x)(CoPt)_(x)(0.8 nm)/Co shown in FIG. 21. Althoughnon-collinear coupling may not be observed with a coupling layer ofpurely Ru_(1-x)Pd_(x) or Ru_(1-x)Pt_(x) (e.g. no second group element24), if coupling layer 20 is thin enough such that Co (or some othermagnetic elements) inter-diffuses into coupling layer 20 from the outermagnetic layers 30, 40, non-collinear coupling may be achievable. Such aphenomenon is depicted in FIG. 21. Where the coupling layer 20 isrelatively thick (e.g. for the structure ofCo(t_(m1))/Ru_(1-x)Pd_(x)(1.2 nm)/Co((t_(m2)) shown in FIG. 21), a sharptransition from antiferromagnetic to ferromagnetic coupling is observedwith almost no non-collinear coupling. On the other hand, where couplinglayer 20 is relatively thin (e.g. for the structure ofCo(t_(m1))/Ru_(1-x)Pd_(x)(0.8 nm)/Co((t_(m2)) shown in FIG. 21), theRu_(1-x)Pd_(x) coupling layer 20 is thin enough for Co to inter-diffusethroughout its thickness such that the coupling layer 20 actuallycomprises Ru_(1-y)(CoPd)_(y) where y>x and non-collinear coupling anglesφ are observed. Thus, the addition of Pd or Pt in a thin Ru couplinglayer 20 may assist in the occurrence of non-collinear coupling betweenCo magnetic layers 30, 40. The addition of Pd or Pt in a thin Rucoupling layer 20 may also assist in the occurrence of non-collinearcoupling between non-Co magnetic layers 30, 40. For magnetic structures10 where coupling layer 20 is thin, Pd and Pt may be added to couplinglayer 20 to achieve non-collinear coupling.

FIG. 22 depicts the dependence of coupling angle φ on coupling layerthickness t_(c) for a number of magnetic structures 10 ofCo/Ru_(1-x)Mn_(x)(0.8 nm)/Co for x values of 73.5, 77.6, 79.8 and 100.For t_(c) of less than or equal to 1.2 nm, pure (or relatively pure) Mndisplays ferromagnetic coupling while for greater than 1.4 nm, pure (orrelatively pure) Mn displays orthogonal non-collinear coupling. Oneexplanation for the difference in behaviour for t_(c) is less than orequal to 1.2 nm and for t_(c) is equal to or greater than 1.4 nm couldbe that for lower values of t_(c), there is diffusion of Co frommagnetic layers 30, 40 into coupling layer 20 whereas for higher valuesof t_(c), there is little to no effect caused by such diffusion.

For magnetic structures 10 of Co/Ru_(1-x)Mn_(x)(t_(c))/Co where x isgreater than 73.5 and less than 79.8, non-collinear coupling is observedfor t_(c) is greater than 0.6 nm and less than 2.0 nm. For magneticstructures 10 of Co/Ru_(1-x)Mn_(x)(t_(c))/Co where x is 73.5 or 79.8,non-orthogonal non-collinear coupling is achievable for t_(c) below 1.6nm (likely due to diffusion of magnetic material from magnetic layers30, 40 into the relatively thin coupling layer 20) while above t_(c) of1.6 nm, orthogonal non-collinear coupling is observed (likely due to thelow “effective” concentration of magnetic material that diffuses intothe Mn coupling layer 20 from the magnetic layers 30, 40—the low“effective” concentration because of the relatively large coupling layer20 thickness t_(c)). Similarly, for magnetic structures 10 ofCo/Ru_(1-x)Mn_(x)(t_(c))/Co where x is 77.6, non-orthogonalnon-collinear coupling is achievable for t_(c) below 1.4 nm (likely dueto diffusion of magnetic material from magnetic layers 30, 40 into therelatively thin coupling layer 20) while above 1.4 nm, orthogonalnon-collinear coupling is observed (likely due to the low “effective”concentration of magnetic material that diffuses into the Mn couplinglayer 20 from the magnetic layers 30, 40).

While a coupling layer 20 of pure (or relatively pure) Mn may achieveorthogonal non-collinear coupling, non-collinear coupling is no longerobserved when a small amount of a magnetic element is added to the pure(or relatively pure) Mn coupling layer 20. This can be observed in FIG.22 below t_(c)=0.12 nm due to the diffusion of Co. This was alsoexperimentally observed with a magnetic structure 10 of Co/Mn₉₆Fe₄(1.4nm)/Co, for which non-collinear coupling was not observed. Furthermore,it is not possible to anneal structures having a coupling layer 20 ofpure (or relatively pure) Mn, while maintaining non-collinear couplingsince annealing encourages diffusion of magnetic material from first andsecond magnetic layers 30, 40 into coupling layer 20. For example, amagnetic structure 10 of Co/Mn(1.6 nm)/Co was created and was found toexhibit orthogonal non-collinear coupling. However, after magneticstructure 10 of Co/Mn(1.6 nm)/Co was annealed at 200° C., non-collinearcoupling was no longer observed (see FIG. 1).

In some embodiments, it may be desirable to include two or more secondgroup elements 24 (e.g. two magnetic elements) in a coupling layer 20.For example, it may be desired to include both Fe and Co, Fe and Ni, orCo and Ni in a coupling layer 20. Further, it may be desirable toinclude Fe and Mn, Co and Mn, or Ni and Mn.

FIG. 23 depicts the dependence of coupling angle φ on atomicconcentration parameter x for various magnetic structures 10 such asCo/Ru_(1-x)(Fe₅₀Co₅₀)_(x)(0.55 nm)/Co. Of note, the plotted values foras Co/Ru_(1-x)(Fe₅₀Co₅₀)_(x)(0.55 nm)/Co fall between the plotted valuesfor Co/Ru_(1-x)Fe_(x)(0.75 nm)/Co and Co/Ru_(1-x)Co_(x)(0.75 nm)/Co. Itis expected that such a relationship would hold true for other magneticstructures having two second group elements 24 (e.g. two magneticelements). For example, it is expected that the values forCo/Ru_(1-x)(Fe_(y)Ni_(100-y))_(x)(t_(c))/Co would fall between theplotted values for Co/Ru_(1-x)Fe_(x)(t_(c))/Co andCo/Ru_(1-x)Ni_(x)(t_(c))/Co, that the values forCo/Ru_(1-x)(Co_(y)Ni_(100-y))_(x)(t_(c))/Co would fall between theplotted values for Co/Ru_(1-x)Co_(x)(t_(c))/Co andCo/Ru_(1-x)Ni_(x)(t_(c))/Co, that the values forCo/Ru_(1-x)(Fe_(y)Mn_(100-y))_(x)(t_(c))/Co would fall between theplotted values for Co/Ru_(1-x)Fe_(x)(t_(c))/Co andCo/Ru_(1-x)Mn_(x)(t_(c))/Co, etc. It is also expected that as y isincreased for each of these structures, the coupling layer 20 and theresultant magnetic structure 10 will behave (in regard to the couplinglayer 20 thickness t_(c) for which non-collinear coupling is achievedfor each value of x and the coupling angle φ that would be achieved foreach value of x) more closely to a coupling layer having only theelement for which the concentration is increased. For example, for astructure of Co/Ru_(1-x)(Co_(y)Ni_(100-y))_(x)(t_(c))/Co, an increase iny would make the structure behave more closely toCo/Ru_(1-x)(Co)_(x)(t_(c))/Co and, correspondingly, a decrease in ywould make the structure behave more closely toCo/Ru_(1-x)(Ni)_(x)(t_(c))/Co. Furthermore, it is expected that thefirst group element 22 (e.g. Ru in the above-discussed examples) couldbe replaced with other first group elements 22 with similar effect.

For example, in the case of Co/Ru_(1-x)(Fe_(y)Mn_(100-y))_(x)(t_(c))/Co,as y is increased, coupling layer 20 will behave more likeCo/Ru_(1-x)Fe_(x)(t_(c))/Co and if y is decreased, coupling layer 20will behave (in regard to the coupling layer 20 thickness t_(c) forwhich non-collinear coupling is achieved for each value of x and thecoupling angle φ that would be achieved for each value of x) more likeCo/Ru_(1-x)Mn_(x)(t_(c))/Co. This is discussed in more detail below inrelation to FIGS. 24, 25 and 26.

FIGS. 24 and 25 depict the dependence of bilinear coupling strength, J₁,and biquadratic coupling strength, J₂, on the atomic concentrationparameter, y, for magnetic structures of Co/Ru₂₂(Fe_(100-y)Mn_(y))₇₈/Co,Co/Ru₂₃(Fe_(100-y)Mn_(y))₇₇/Co, Co/Ru₂₇(Fe_(100-y)Mn_(y))₇₃/Co andCo/Ru₃₁(Fe_(100-y)Mn_(y))₆₉/Co. As can be seen from FIGS. 24 and 25, themagnitudes of bilinear coupling strength, J₁, and biquadratic couplingstrength, J₂, decrease as the atomic concentration parameter, y,increases (e.g. as coupling layer 20 becomes more like RuMn and lesslike RuFe). While non-collinear coupling at various angles φ may stillbe achieved with values of atomic concentration parameter, y, greaterthan 68 and less than 80 (as can be seen by comparing magnetic structure10 of Co/RuMn(t_(c))/Co to magnetic structure 10 of Co/RuFe(t_(c))/Co inFIG. 22), the coupling strength decreases as the atomic concentrationparameter, y, increases (i.e. as the amount of Mn increases).Non-collinear, non-orthogonal coupling of magnetic structure 10 ofCo/RuMn(t_(c))/Co may be achieved due to diffusion of Co from magneticlayers 30, 40 into coupling layer 20 when coupling layer 20 issufficiently thing (e.g. t_(c) is sufficiently low) that diffusion canoccur throughout the entire (or close to the entire) thickness, t_(c),of coupling layer 20.

FIG. 26 depicts the dependence of saturation field on atomicconcentration parameter, y, for magnetic structures 10 ofCo/Ru₂₂(Fe_(100-y)Mn_(y))₇₈/Co, Co/Ru₂₃(Fe_(100-y)Mn_(y))₇₇/Co,Co/Ru₂₇(Fe_(100-y)Mn_(y))₇₃/Co and Co/Ru₃₁(Fe_(100-y)Mn_(y))₆₉/Co. Ascan be seen from FIG. 26, the magnitude of the saturation field of themagnetic structures decreases as the atomic concentration parameter yincreases (i.e. as the amount of Mn increases).

Although not mandatory and unless otherwise specified, first and secondmagnetization directions 32, 42 of the example embodiments andexperimental results discussed in this section are “in-plane”magnetization directions—that is that first and second magnetizationdirections 32, 42 extend in an XY plane and do not extend substantiallyin the Z-direction. It should be understood that first and secondmagnetization directions 32, 42 (or some component thereof) could extendin the Z-direction, however, the resultant coupling angles may vary dueto anisotropy of first and second magnetic layers 32, 42. Most magneticmaterials have magnetic anisotropy. There are several sources ofmagnetic anisotropy such as: shape anisotropy due to material shape,surface anisotropy due to change in the symmetry between two materials,magnetocrystalline anisotropy due to spin orbital coupling and symmetryfrom crystal structure, and magnetoelastic anisotropy induced byexpansion or contraction of magnetic material. The magnetic anisotropymay modify the coupling angle between first and second magnetizationdirection 32, 42. Magnetic anisotropy can therefore be taken intoconsideration to obtain a desired coupling angle between magneticmoments 32, 42 of magnetic layers 30, 40. In addition, magnetic fieldsthat are produced by other magnetic materials or external fields mayalso change the coupling angle between magnetic moments 32, 42 ofmagnetic layers 30, 40.

Applications

Magnetic structure 10 and/or coupling layer 20 may be incorporated intomany different applications or devices such as sensors, magnetic memory,oscillators, diodes, microwave detectors, temperature sensors, energyharvesters or combinations of two or more of the above applications ordevices. Devices that incorporate magnetic structure 10 and/or couplinglayer 20 may be reduced in size as compared to prior art devices, mayrequire less energy as compared to prior art devices as describedherein, may be more reliable as compared to prior art devices and/or maybe faster than prior art devices.

In some embodiments, magnetic structure 10 and/or coupling layer 20 asdescribed herein is incorporated into a sensor. By incorporatingmagnetic structure 10 into a sensor, magnetic structure 10 may serve toreplace antiferromagnetic pinning layers traditionally used in magneticsensors and may thereby reduce the size of such sensors. Magneticstructure 10 may allow for stronger magnetic coupling between magneticlayers of the sensor which in turn increases the range of appliedmagnetic fields that may be sensed by such a sensor. Magnetic structure10 may also allow for easier fabrication of sensors and may reduce oreliminate a need for annealing steps normally involved in fabrication ofprior art sensors.

The following magnetic devices (e.g. magnetic devices 100, 200, 300,400, 500 etc.) may be employed as or as part of sensors, magneticmemory, oscillators, diodes, microwave detectors, temperature sensors,energy harvesters, combinations of two or more of the above and/or otherdevices used for other applications. In some circumstances, one or moreof the following magnetic devices are described in the context of asensor or of a magnetic memory device in order to provide a more fulldisclosure of how a particular magnetic device may be employed. However,it should be understood that each of the following devices (e.g.magnetic devices 100, 200, 300, 400, 500 etc.) can nonetheless beemployed as or as part of sensors, magnetic memory, oscillators, diodes,microwave detectors, temperature sensors, energy harvesters,combinations of two or more of the above and/or other devices used forother applications.

Magnetic structures 10, and/or coupling layers 20 disclosed herein maybe employed in a device to, for example, set a free magnetizationdirection of the device at a non-collinear angle with respect to other(free or fixed) magnetization directions within the device, to set afixed magnetization direction of the device at a non-collinear anglewith respect to other magnetization directions within the device, or toset a free magnetization direction of the device at a non-collinearangle with respect to a fixed magnetization direction of the device. Byemploying magnetic structure 10, and/or coupling layer 20 as describedherein, it may be possible to achieve stable states at angles that wouldnot otherwise be possible, such as in FIG. 28 described further herein.

FIG. 27A is a schematic diagram of a magnetic device 100 according toone aspect of the invention. In some embodiments, magnetic device 100may be used as, or as part of, a sensor. Magnetic device 100 comprises amagnetic structure 110 that may be substantially similar to any magneticstructures 10 described herein. Magnetic structure 110 comprises a firstmagnetic layer 130, a coupling layer 120, and a second magnetic layer140. First magnetic layer 130 of magnetic device 100 has a firstmagnetization direction 132, second magnetic layer 140 has a secondmagnetization direction 142. First and second magnetic layers 130, 140are coupled to one another across coupling layer 120, such that theirrespective magnetization directions 132, 142 are oriented at anon-collinear angle, φ, with respect to one another in the absence of anexternal applied magnetic field. Magnetic device 100 may also optionallycomprise a magnetoresistive layer 160 separating a second magnetic layer140 and a third magnetic layer 170. Together, first magnetic layer 130,coupling layer 120, second magnetic layer 140, magnetoresistive layer160 and third magnetic layer 170 may be referred to as body 112 ofdevice 100 (or device body 112). In practice, magnetic device 100 may beused to detect externally applied magnetic fields by measuring changesof resistance across body 112 due to effects on magnetic device 100caused by applied magnetic fields—e.g. external magnetic fields in avicinity of device 100.

Third magnetic layer 170 may be substantially similar to one or both offirst and second magnetic layers 130, 140, although this is notmandatory. Third magnetic layer 170 has a third magnetization direction172.

Magnetoresistive layer 160 may optionally be employed to amplifyresistance changes across magnetic device 100. Magnetoresistive layer160 is not mandatory as magnetic structure 10 itself may exhibit changesin resistance in response to externally applied magnetic fields.However, such changes in resistance of magnetic structure 10 may berelatively small and it may be beneficial to employ magnetoresistivelayer 160. Magnetoresistive layer 160 may comprise any suitablemagnetoresistive material that amplifies changes in electricalresistance across body 112 in response to changes in the relative anglebetween magnetization direction 142 and magnetization direction 172. Forexample, magnetoresistive layer 160 may comprise a conductivemagnetoresistive layer such as but not limited to Cu, Cr, Ru, Al, Ag,and alloys thereof in addition to magnetoresistive layers that arecommonly used for GMR or a non-conductive magnetoresistive layer suchas, but not limited to, magnesium oxide (MgO) and aluminum oxide(AlO_(x)) in addition to magnetoresistive layers that are commonly thatare used for TMR.

First magnetization direction 132 may be described as being “fixed” ascompared to second magnetization direction 142 which may be described asbeing “free”. In other words, second magnetization direction 142 maychange directions in response to an externally applied magnetic fieldhaving a first magnitude, a, while first magnetization direction 132would remain constant in response to the externally applied magneticfield having the first magnitude, a. In practice, as used throughoutthis description and the accompanying claims, unless the contextdictates otherwise, a magnetization direction that is “constant” or“fixed” may actually vary or fluctuate by a small amount but maintainssubstantially the same orientation in response to applied magneticfield, a, when compared to corresponding changes in the “free”magnetization direction in response to the same applied magnetic field,a. First magnetization direction 132 (the “fixed” magnetizationdirection of the FIG. 27A embodiment), might only change direction inresponse to an externally applied magnetic field greater or equal to asecond magnitude, b, where b is greater than a. In some embodiments, bis substantially greater than a. For example, b may be double a or b maybe an order of magnitude greater than a.

Like first magnetization direction 132, third magnetization direction172 may also be fixed as compared to second magnetization direction 142.Like first magnetization direction 132, third magnetization direction172 would remain substantially constant in response to the externallyapplied magnetic field having the first magnitude, a, and might onlychange in response to an externally applied magnetic field greater orequal to a third magnitude, c, wherein c is greater than a. The thirdmagnitude, c, may be greater than, less than or equal to the secondmagnitude, b.

In practice, it is preferable that magnetic device 100 is employed inthe presence of external magnetic fields having a magnitude less thaneach of the second and third magnitudes, b and c. Accordingly, unlessthe context dictates otherwise, when a magnetization direction isdiscussed herein as being “fixed”, the magnetization direction will notchange appreciably in the presence of an applied magnetic field, wherethe applied magnetic field has a magnitude less than the operatinglimits of the device. On the other hand, unless the context dictatesotherwise, when a magnetization direction is discussed herein as being“free”, the magnetization direction may be changeable in the presence ofan applied magnetic field where the applied magnetic field has amagnitude less than the operating limits of the device.

Any suitable apparatus or method may be employed to fix first and thirdmagnetization directions 132, 172. For example, the materials of firstand third magnetic layers 130, 170 may be chosen such that magnetizationdirections 132, 172 are fixed while second magnetization direction 142is free. Alternatively, additional magnetic layers may beferromagnetically coupled or coupled by a coupling layer (e.g.ferromagnetically, antiferromagnetically or non-collinearly coupled) toone or both of first and third magnetic layers 130, 170 to thereby fixfirst and third magnetization directions 132, 172. In some embodiments,a secondary applied field may be applied to fix one or more of first andthird magnetization directions 132, 172.

The angular difference between first and second magnetization directions132, 142 may be described as first angle, α, and the angular differencebetween first and third magnetization directions 132, 172 may bedescribed as second angle, β.

In some embodiments, in the absence of applied field or heat, firstangle, α is approximately 90° and second angle, β is approximately 180°.Such embodiments, may improve the sensitivity of magnetic device 100since the change in resistance of magnetic device 100 is relatively morelinear when second and third magnetization directions 142, 172 are at90° with respect to one another. In other embodiments, first angle, αand second angle, β are not equal to 90° and 180° respectively but maybe chosen such that second and third magnetization directions 142, 172are at 90° with respect to one another.

Although the FIG. 27A embodiment of magnetic device 100 depicts firstand second and third magnetization directions 132, 142, 172 as extendingwithin the X-Y plane, this is not mandatory. First and second and thirdmagnetization directions 132, 142, 172 may have any combination of X, Yand Z components.

A circuit 195 may be connected to first and third magnetic layers, 130,170 to measure a resistance across body 112, as is known in the art.Circuit 195 may include any suitable resistance measuring component(s)to measure resistance across body 112 of magnetic device 100.

When the angle between second magnetization direction 142 and thirdmagnetization direction 172 changes in response to any applied magneticfield having a first magnitude, a (less than the second and thirdmagnitudes, b and c), a resultant change in resistance of body 112occurs. The resultant change in resistance of body 112 may optionally bemagnified due magnetoresistive layer 160 located between second andthird magnetic layers 140, 170. Magnetic device 100 can be used todetermine the presence and/or direction and/or magnitude of an appliedmagnetic field by measuring the resistance across body 112. In someembodiments, magnetoresistive layer 160 is not employed and theresistance across body 112 may still be measured, although the change inresistance may be smaller.

In some embodiments, magnetic device 100 may be employed as atemperature sensor. FIG. 27B is a plot depicting the relationship of thenon-collinear coupling angle, α, between first and second magneticlayers 130, 140 on temperature. As can be seen from FIG. 27B, thenon-collinear coupling angle, α, between first and second magneticlayers 130, 140 may be temperature dependent. The solid line withdiamonds represents a first sample configured to detect temperaturesbelow 300K. The first sample comprised a Ru_(100-x)Co_(x) coupling layer120. The solid line with circles represents a second sample configuredto detect temperatures near 300K. The second sample comprised aRu_(100-x)Co_(x) coupling layer 120 where x is different than for thefirst sample. The solid line with triangles represents an extrapolationof the second sample data based on the first sample data for highertemperatures than have been measured for the second sample. Since thenon-collinear coupling angle, α, between first and second magneticlayers 130, 140 changes with changes in temperature and the resistanceof magnetic device 100 changes with changes in the non-collinearcoupling angle, α, between first and second magnetic layers 130, 140,the temperature of magnetic device 100 may be determined based onchanges in resistance of magnetic device 100. Temperature magneticdevice 100 may be configured for different temperature ranges bychanging the atomic concentration parameter, x, of coupling layer 120,the coupling layer 120 thickness, t_(c), the coupling layer 120composition, the magnetic layer 30, 40 thickness t_(m1), t_(m2), or themagnetic layer 30, 40 composition as discussed herein such that a linearor generally linear region of the dependence of coupling angle, α, ontemperature is centered or near-centered on a desired temperature range.

In some embodiments, magnetic structures 10 and/or coupling layers 20disclosed herein may be incorporated into a magnetic memory device. Amagnetic memory device incorporating magnetic structure 10 may functionwith reduced current (relative to prior art devices withoutnon-collinearly coupled magnetic structure 110) to switch between statesand may have greater reliability of switching (relative to prior artdevices without non-collinearly coupled magnetic structure 110).Moreover, switching between states may require less time and/or currentdue to the smaller change in angle required between states, as comparedto prior art magnetic memory devices (without non-collinearly coupledmagnetic structure 110).

FIG. 28 is a schematic diagram of a magnetic device 200 according to oneembodiment of the invention. Magnetic device 200 may be employed as amemory device. Magnetic device 200 may be substantially similar tomagnetic device 100 except as described below. For example, magneticdevice 200 comprises a magnetic structure 210 similar to magneticstructure 110, first, second and third magnetic layers 230, 240, 270having first, second and third magnetization directions 232, 242, 272similar to first, second and third magnetic layers 130, 140, 170 havingfirst, second and third magnetization directions 132, 142, 172, a firstcoupling layer 220 similar to coupling layer 120, a magnetoresistivelayer 260 similar to magnetoresistive layer 160 and circuit 295 similarto circuit 195. Magnetic device 200 differs from magnetic device 100 inthat it also includes an optional second coupling layer 280 and anoptional fourth magnetic layer 290. In the illustrated embodiment,second coupling layer 280 and fourth magnetic layer 290 are employed tofix first magnetization direction 232 and may be replaced by any othersuitable mechanism for fixing first magnetization direction 232.Together, first, second, third and fourth magnetic layers 230, 240, 270,290, first and second coupling layers 220, 280, and magnetoresistivelayer 260 may be referred to as body 212 of device 200 (or device body212).

Fourth magnetic layer 290 may be substantially similar to any of themagnetic layers disclosed herein (e.g. magnetic layers, 30, 40, 70, 130,140, 170, 230, 240, 270, etc.), although this is not mandatory.

Coupling layer 220 may be substantially similar to any of the couplinglayers disclosed herein (e.g. coupling layer 20, 120, etc.), althoughthis is not mandatory.

First and second magnetic layers 230, 240 may be non-collinearly coupledin a first state in which the first magnetization direction 232 isoriented at θ° (e.g. in a clockwise direction) relative to the secondmagnetization direction or a second state in which the firstmagnetization direction 232 is oriented at −θ° (e.g. in acounter-clockwise direction) relative to the second magnetizationdirection.

First magnetization direction 232 may be fixed as compared to secondmagnetization direction 242 which may be described as being free. Likefirst magnetization direction 232, third magnetization direction 272 mayalso be fixed as compared to second magnetization direction 242.

Any suitable apparatus or method may be employed to fix first and thirdmagnetization directions 232, 272. For example, the materials of firstand third magnetic layers 230, 270 may be chosen such that magnetizationdirections 232, 272 are fixed. Alternatively, additional magneticlayers, such as fourth magnetic layer 290 may be coupled by a couplinglayer such as second coupling layer 280 to one or both of first andthird magnetic layers 230, 270 to thereby fix first and thirdmagnetization directions 232, 272.

In FIG. 28, first and second magnetization directions 232, 242 aredepicted as being in-plane (e.g. in an XY plane defined by the X and Ydirections). This is not mandatory. First and/or second magnetizationdirections 232, 242 may extend partially or completely in the Zdirection or one or more of first and second magnetization directions232, 242 may extend in some combination of the X, Y and Z directions.For example, FIG. 30A depicts first and second magnetization directions432, 442 that extend out of the XY plane.

Second magnetization direction 242 of second magnetic layer 240 can becaused to change between its first and second states by spin torquetransfer (e.g. applying a current through circuit 295). By passing thecurrent through third magnetic layer 270, electric current is polarized.By passing the polarized current through second magnetic layer 240, thepolarized current may cause the second magnetic layer 240 to change fromits first stable state to its second stable state (or vice versa). Theamount of charge for second magnetic layer 240 to change between itsstates may depend on the angular difference between the first and secondstates of second magnetic layer 240. The charge may be reduced byreducing the angular difference between the first and second states ofsecond magnetic layer 240. Reducing the angular difference between thefirst and second states of second magnetic layer 240 may be accomplishedwith non-collinear coupling (e.g. by employing magnetic structure 10and/or coupling layer 20, as described herein). In some embodiments, byreducing the angular difference between the first and second states ofsecond magnetic layer 240, the switching time between states maycorrespondingly decrease (i.e. switching will be faster). Therefore, insome embodiments, it may be desirable reduce the angular differencebetween the first and second states of second magnetic layer 240 toachieve suitably fast switching times for a desired application.Conversely, increasing the angular difference between the first andsecond states of second magnetic layer 240 may increase the differencebetween the resistance across magnetic device 200 in the first state ofsecond magnetic layer 240 and the resistance across magnetic device 200in the second state of second magnetic layer 240. Therefore, in someembodiments, it may be desirable to increase the angular differencebetween the first and second states of second magnetic layer 240 toachieve sufficiently large resistance changes between states for adesired application.

By coupling first and second magnetization directions 232, 242 at anon-collinear angle, the amount of current to change second magneticlayer 240 between its first and second states may be reducedconsiderably as compared to ferromagnetic coupling and/orantiferromagnetic coupling. Moreover, the time to switch between stablestates may be reduced and the reliability of switching of magneticdevice 200 may be relatively greater than prior art devices which do nothave non-collinearly coupled structure 210.

When second magnetic layer 240 is in its first state, the resistanceacross body 212 (as can be measured by circuit 295) may have a firstvalue. When second magnetic layer 240 is in its second state, theresistance across body 212 (as can be measured by circuit 295) may havea second value, different from the first value. Therefore, bydetermining the resistance across body 112 (as can be measured bycircuit 295), it is possible to determine the state of second magneticlayer 240. Information such as a bit can therefore be stored on magneticdevice 200. For example, the first state of second magnetic layer 240(and its associated first value of resistance) could correspond to a “0”bit and the second state of second magnetic layer 240 (and itsassociated second value of resistance) could correspond to a “1” bit.

Additional layers may be added to magnetic device 200 to allowadditional information to be stored in magnetic device 200. For example,FIG. 29 is a schematic depiction of a magnetic device 300 according toanother embodiment of the invention. Magnetic device 300 issubstantially similar to magnetic device 200 except in that it comprisestwo magnetic devices 200-1, 200-2 stacked on top of one another whereina third magnetic layer 270-1 of the first magnetic device 200-1 alsoserves as a fourth magnetic layer 290-2 of the second magnetic device200-2.

By stacking two magnetic memory devices 200-1, 200-2 on top of oneanother, magnetic device 300 may have four separate states that couldrepresent information stored on magnetic device 300. In particular,magnetic device 300 may have:

-   -   state A in which the second magnetic layer 240-1 of the first        magnetic device 200 is in a first state and the second magnetic        layer 240-2 of the second magnetic device 200 is in a first        state;    -   state B in which the second magnetic layer 240-1 of the first        magnetic device 200 is in a first state and the second magnetic        layer 240-2 of the second magnetic device 200 is in a second        state;    -   state C in which the second magnetic layer 240-1 of the first        magnetic device 200 is in a second state and the second magnetic        layer 240-2 of the second magnetic device 200 is in a first        state; and    -   state D in which the second magnetic layer 240-1 of the first        magnetic device 200 is in a second state and the second magnetic        layer 240-2 of the second magnetic device 200 is in a second        state.

First magnetic layer 240-1 may use a different switching current (and/ordifferent switching current characteristics) to switch between its firstand second states as compared to second magnetic layer 240-2.Accordingly, the state of second magnetic layer 240-1 may be changedindependently of the state of second magnetic layer 240-2. The switchingcurrent for first magnetic layer 240-1 may differ from the switchingcurrent for second magnetic layer 240-1 in that the polarization couldbe different, the amount of time during which the current is appliedcould be different, etc. In some embodiments, the switching current isdependent upon the magnitude of the change of angle between first andsecond states (e.g. more current may be required to change betweenstates that have a larger angular difference). The magnitude of thechange of angle between first and second states may be reduced byemploying non-collinear coupling (e.g. by employing magnetic structures10 and/or coupling layer 20) relative to prior art devices which do nothave non-collinearly coupled structures 210.

While FIG. 29 depicts a magnetic device 300 having two layers ofmagnetic devices 200, it should be understood that more than two layersof devices 200 can be stacked to create more complex memory states. Forexample, with three magnetic devices 200 stacked on top of one another,there would be eight possible memory states. As more layers are added,the potential number of memory states increases by a power of two.

Magnetic structures 10 and/or coupling layers 20 may be employed in anoscillator device, diodes, microwave detectors, energy harvesters and/orother devices. By employing magnetic structure 10 and/or coupling layer20, it may be possible to align a free magnetization direction with aprecession angle of a magnetic layer to allow for precession of the freemagnetization direction. In some embodiments, non-orthogonalnon-collinear coupling is employed to align a free magnetizationdirection with a precession angle of a magnetic layer to allow forprecession of the free magnetization direction. Without non-orthogonalnon-collinear coupling, it would be difficult to achieve precession ofthe free magnetization direction.

FIG. 30A is a schematic diagram depicting a magnetic device 400according to a non-limiting embodiment of the invention. Magnetic device400 may be employed as an oscillator. Magnetic device 400 may besubstantially similar to magnetic device 100 except as described herein.Magnetic device 400 comprises a magnetic structure 410 similar tomagnetic structure 110, first, second and third magnetic layers 430,440, 470 having first, second and third magnetization directions 432,442, 472 similar to first, second and third magnetic layers 130, 140,170, a first coupling layer 420 similar to coupling layer 120, amagnetoresistive layer 460 similar to magnetoresistive layer 160, a body412 similar to body 112 and circuit 495 similar to circuit 195. Magneticdevice 400 differs from magnetic device 100 in that the first, secondand third magnetization directions 432, 442, 472 may be different thanthe first, second, and third magnetization directions 132, 142, 172, asdiscussed further herein.

In the FIG. 30A embodiment, first and third magnetization directions432, 472 are fixed while second magnetization direction 442 is free.

First and second magnetization directions 432, 442 are coupled to oneanother across coupling layer 420 such that their respectivemagnetization directions 432, 442 are oriented at a non-collinear anglewith respect to one another in the absence of an external appliedmagnetic field wherein the non-collinear angle is such that secondmagnetization direction 442 is aligned with, or approximately alignedwith, a precession angle of second magnetic layer 440. To align secondmagnetization direction 442 with the precession angle of second magneticlayer 440, second magnetization direction 442 may be chosen based on thematerial of second magnetic layer 440, the thickness of second magneticlayer 440 or the desired operating current.

In some embodiments, in the absence of applied magnetic field, heat,etc. third magnetization direction 472 is non-parallel with firstmagnetization direction 432. In some embodiments, third magnetizationdirection 472 is orthogonal to first magnetization direction 432. Insome embodiments, a difference between first magnetization direction 432and second magnetization direction 442 remains relatively constant evenas second magnetization direction 442 changes. On the other hand, adifference between third magnetization direction 472 and secondmagnetization direction 442 changes as second magnetization direction442 changes.

When a current is applied to magnetic device 400 by circuit 495, thespin torque of the current causes second magnetization direction 442 toprecess around a precession axis. In some embodiments, the precessionaxis is parallel or almost parallel with the Z-direction, although thisis not mandatory. As second magnetization direction 442 precesses, itsangular relationship with third magnetization direction 472 changes. Insome positions along its precession, a component of second magnetizationdirection 442 points in the same direction as third magnetizationdirection 472 while in other positions along its precessions, nocomponent of second magnetization direction 442 points in the samedirection as third magnetization direction 472. As second magnetizationdirection 442 precesses, the resistance across body 412 changes. Thischange may optionally be amplified by magnetoresistive layer 460. Duringone precession of magnetization direction 442, the resistance goes froma minimum (when a component of second magnetization direction 442 pointsin the same direction as third magnetization direction 472) and amaximum (when no component of second magnetization direction 442 pointsin the same direction as third magnetization direction 472). Asmagnetization direction 442 precesses, the resistance cycles throughthis minimum and maximum. This cyclic change in resistance across body412 can be used to create an oscillating signal in circuit 495. Byemploying magnetic structure 410, the amount of current and/or appliedexternal field to induce precession may be reduced relative to prior artdevices that do not use non-collinearly coupled structure 410.

FIG. 30B is a schematic diagram depicting a magnetic device 500according to a non-limiting embodiment of the invention. Magnetic device500 may be employed as an oscillator. Magnetic device 500 issubstantially similar to magnetic device 400 except as described herein.Magnetic device 500 comprises a magnetic structure 510 similar tomagnetic structure 410, first, second and third magnetic layers 530,540, 570 having first, second and third magnetization directions 532,542, 572 similar to first, second and third magnetic layers 430, 440,470, a first coupling layer 520 similar to coupling layer 420, amagnetoresistive layer 560 similar to magnetoresistive layer 460, anbody 512 similar to body 412 and circuit 595 similar to circuit 495.

Magnetic device 500 differs from magnetic device 400 in that firstmagnetization direction 532 is free while first magnetization direction432 is fixed. Although FIG. 30B shows that first magnetization direction532 and second magnetization direction 542 are precessing at similar(but opposite) angles, this is not necessary and first and secondmagnetization directions 532, 542 may precess at different angles. Insome embodiments, current may be passed through magnetic device 500 inopposite directions or different currents or currents having differentcharacteristics may be passed through magnetic device 500 to cause firstand second magnetization directions 532, 542 to precess at differentfrequencies.

FIG. 30C is a schematic diagram depicting a magnetic device 600according to a non-limiting embodiment of the invention. Magnetic device600 is substantially similar to magnetic device 500 except as follows.Magnetic device 600 comprises a magnetic structure 610 similar tomagnetic structure 510, first, second and third magnetic layers 630,640, 670 having first, second and third magnetization directions 632,642, 672 similar to first, second and third magnetic layers 530, 540,570, a first coupling layer 620 similar to coupling layer 520, amagnetoresistive layer 660 similar to magnetoresistive layer 560, anbody 612 similar to body 512 and circuit 595 similar to circuit 595.

Magnetic device 600 differs from magnetic device 500 in that secondmagnetization direction 642 is limited in the X-Y plane while secondmagnetization direction 542 extends out of the X-Y plane. Since thirdmagnetization direction 672 is also fixed in the X-Y plane, it ispossible that second and third magnetization directions 642, 672 may beoriented at 0° and 180° relative to one another thereby leading tolarger changes in resistance across body 612 as compared to bodies 412,512 and larger amplitude oscillations of the signal as compared tomagnetic devices 400, 500.

While the above embodiments discuss applying direct current to magneticdevices 400, 500, 600, in some embodiments, the current applied tomagnetic devices 400, 500, 600 may be oscillating. In such embodiments,when the oscillation frequency is within the corresponding oscillationfrequency range of magnetic devices 400, 500, 600, the signal producedby magnetic devices 400, 500, 600 may be direct current.

In another application, a magnetic field could be applied to magneticdevice 400 (or any of magnetic devices 500, 600) to cause or assistmagnetization direction 442 to oscillate. As magnetization direction 442oscillates due to the applied magnetic field or is assisted inoscillation by the applied magnetic field, the magnetoresistive effectsof magnetoresistive layer 460 may be used to power or add power tocircuit 495 and energy is thereby harvested by magnetic device 400 (orany of magnetic devices 500, 600). In some embodiments, the appliedmagnetic field may be the earth's magnetic field.

In some embodiments, magnetic devices 400, 500, 600 may each be employedto sense one or more external magnetic fields. For example, a magneticfield could be applied to device 400 (or any other device herein such asdevices 500, 600) to disrupt, change or distort the oscillation (e.g.the amplitude, frequency or shape of the oscillation) of magnetizationdirection 442. Such disruption, change or distortion of the oscillationof magnetization direction 442 due to the applied magnetic field may becorrelated with an applied magnetic field strength and/or direction. Inthis way a device employed as an oscillator can also be employed as amagnetic field sensor.

In another application, thermal fluctuations could be employed to causeor assist magnetization direction 442 of magnetic device 400 (or one ofmagnetization directions 542, 642 of magnetic devices 500, 600respectively) to oscillate. As magnetization direction 442 oscillatesdue to the thermal fluctuations or assisted by the thermal fluctuations,the magnetoresistive effects of magnetoresistive layer 460 may be usedto power or add power to circuit 495 and energy is thereby harvested bymagnetic device 400 (or one of magnetic devices 500, 600). In someembodiments, the thermal fluctuations could be combined with an appliedmagnetic field or/and an applied current to cause magnetizationdirection 442 to oscillate.

In some embodiments, one or more of magnetic device 100, magnetic device200 (and/or 300), magnetic device 400 (and/or 500, 600) may be combinedto form a single device by stacking two or more such devices on top ofanother in a similar fashion to the way that magnetic device 300comprises two magnetic devices 200 stacked on top of one another. Insome such embodiments, two or more of the stacked devices may share oneor more magnetic layers, coupling layers, and/or magnetoresistivelayers, although this is not mandatory.

FIGS. 31A and 31B are schematic depictions of an oscillator device 702and a memory device 704 combined to form a single device 700 accordingto one embodiment of the invention. Oscillator device 702 may besubstantially similar to magnetic device 500. Magnetic device 700comprises a magnetic structure 710 similar to magnetic structure 510,first, second and third magnetic layers 630, 740, 770 having first,second and third magnetization directions 732, 742, 772 similar tofirst, second and third magnetic layers 530, 540, 570, a first couplinglayer 720 similar to coupling layer 520, a magnetoresistive layer 760similar to magnetoresistive layer 560 and circuit 795 similar to circuit595. Memory device 704 may be substantially similar to memory device200, except as described herein. For example, magnetic memory device 704comprises a magnetic structure 710 similar to magnetic structure 210,first, second and fourth magnetic layers 730, 740, 790 having first,second and fourth magnetization directions 732, 742, 792 similar tofirst, second and third magnetic layers 230, 240, 270 having first,second and third magnetization directions 232, 242, 272, a firstcoupling layer 720 similar to coupling layer 220, a magnetoresistivelayer 780 similar to magnetoresistive layer 260 and circuit 795 similarto circuit 295. Magnetic memory device 704 differs from magnetic device200 in that first magnetization direction 732 may precess.

FIG. 31A depicts a first memory state in which first magnetizationdirection 732 precesses at a first precession angle and FIG. 31B depictsa second memory state in which magnetization direction 732 precesses ata second precession angle. The angular difference between the first andsecond states also corresponds to an angular difference between fourthmagnetization direction 792 and first magnetization direction 732 whichcauses a change in resistance that may be detected by circuit 795. Ineither state, despite the precession of first magnetization direction732, the relationship between fourth magnetization direction 792 andfirst magnetization direction 732 is constant, which allows firstmagnetic layer 732 to be shared by oscillator 702 and magnetic memory704.

Although, magnetic structures 10, 110, 210 etc. and magnetic devices100, 200, 300, 400, 500, 600, 700 are depicted as having rectangular orsquare XY plane cross-sections, this is not necessary. Magneticstructures 10, 110, 210 etc. and magnetic devices 100, 200, 300, 400,500, 600, 700 may have any suitable XY cross-section. In someembodiments, by changing the XY cross-section, magnetization directions(e.g. magnetization directions 32, 42, 132, 142, etc.) may behavedifferently. In some embodiments, the XY plane cross-sectional shape ofa structure or device (e.g. 10, 110, 100, 200 etc.) may be chosen toachieve desired effects on magnetization directions (e.g. magnetizationdirections 32, 42, 132, 142, etc.). For example, it may be desirable toconstruct a memory device having an ellipse XY plane cross-sectionalshape to strengthen stable states. As another example, it may be desiredfor an oscillator to have a circular XY plane cross-sectional shape toassist precession of magnetization direction 442, 542 etc. or to have anellipse XY plane cross-sectional shape to slow down precession ofmagnetization direction 442, 542 etc.

FIG. 32A is a schematic diagram of a magnetic device 800 according toone embodiment of the invention. Magnetic device 800 may be employed as(or as part of), for example, a magnetic memory device, a magneticsensor device, an oscillator device, a diode, a microwave generator oran energy harvesting device.

Magnetic device 800 is substantially similar to magnetic device 100except as described below. Moreover, magnetic device 800 may be employedin the same way that magnetic device 100 may be employed as describedabove and magnetic device 800 may have the same (or some of the same)advantages that magnetic device 100 has as described above in additionto those described below. Magnetic device 800 comprises a magneticstructure 810 similar to magnetic structure 110, first, second and thirdmagnetic layers 830, 840, 870 having first, second and thirdmagnetization directions 832, 842, 872 similar to first, second andthird magnetic layers 130, 140, 170 having first, second and thirdmagnetization directions 132, 142, 172, a first coupling layer 820similar to coupling layer 120, a magnetoresistive layer 860 similar tomagnetoresistive layer 160 and a circuit 895 similar to circuit 195.Together, first, second and third magnetic layers 830, 840, 870, firstcoupling layer 820, and magnetoresistive layer 860 may be referred to asbody 812.

First and second magnetic layers 830, 840 may be non-collinearly coupledsuch that first magnetization direction 832 is oriented at anon-collinear angle with respect to second magnetization direction 842.First magnetization direction 832 is oriented in either the positive Zdirection or the negative Z direction (e.g. orthogonal to the XY plane).First magnetization direction 832 is fixed. Second magnetizationdirection 842 is oriented at least partially in the Z direction and atleast partially in one or both of the X and Y directions. Secondmagnetization direction 842 is fixed at a non-collinear angle withrespect to first magnetization direction 832. It should be understoodthat in some embodiments second magnetization direction 842 may rotateabout a Z direction axis while remaining fixed to first magnetizationdirection 832 at non-collinear angle. As discussed in relation to FIGS.3A and 3B, such rotation could be reduced by elongating the XY-planecross-sectional shape of second magnetic layer 840 in one of the X and Ydirections.

Any suitable apparatus or method may be employed to fix firstmagnetization direction 832. For example, the material of first magneticlayer 830 may be chosen such that magnetization direction 832 is fixed.Alternatively, additional magnetic layers may be ferromagneticallycoupled or coupled by a coupling layer (e.g. ferromagnetically,antiferromagnetically or non-collinearly coupled) to first magneticlayers 830 to thereby fix first magnetization direction 832.

Unlike third magnetization direction 172 of magnetic device 100, thirdmagnetization direction 872 is free relative to first and secondmagnetization directions 832, 842. Specifically, third magnetizationdirection 872 is free to change between a first state wherein thirdmagnetization direction 872 is oriented generally in the positive Zdirection or a second state wherein third magnetization direction 872 isoriented generally in the negative Z direction.

In some embodiments, second magnetic layer 840 of magnetic device 800has an XY-plane cross-section that is elongated in the X direction.Referring back to the discussion of FIG. 3B, the elongated XY-planecross-section may urge or limit the orientation of second magnetizationdirection 842 in the XZ-plane. Therefore, in such embodiments, tomaintain the non-collinear coupling angle between first and secondmagnetization directions 832, 842, second magnetization direction 842 ispractically limited to two possible orientations in the XZ-plane betweenwhich it can “flip”. Alternatively, if magnetic layer 840 has X and Ydirection dimensions that are approximately equal, second magnetizationdirection 842 may have infinite orientations and may be allowed torotate about a Z direction axis, as discussed above in relation to FIG.3A.

Third magnetization direction 872 of third magnetic layer 870 can becaused to change between its first and second states by spin torquetransfer (e.g. applying a current through circuit 895). By passing thecurrent through second magnetic layer 840, the electric current ispolarized. By passing the polarized current through third magnetic layer870, the polarized current may cause the third magnetic layer 870 tochange from its first stable state to its second stable state (or viceversa). The amount of current for changing the state of third magneticlayer 870 may depend on the angular difference between thirdmagnetization direction 872 and second magnetization direction 842. Thecurrent may be reduced by changing the angular difference between thethird magnetization direction 872 and second magnetization direction842. Changing the angular difference between third magnetizationdirection 872 and second magnetization direction 842 may be accomplishedwith non-collinear coupling (e.g. by employing magnetic structure 10and/or coupling layer 20, as described herein) between first and secondmagnetic layers 830, 840. In some embodiments, by changing the angulardifference between third magnetization direction 872 and secondmagnetization direction 842, switching time may be increased andresistance changes between states may be decreased.

By coupling first and second magnetization directions 832, 842 at anon-collinear angle, the amount of current to change third magneticlayer 870 between its first and second states is reduced considerably,as compared to ferromagnetic coupling and/or antiferromagnetic couplingbetween first magnetic layer 830 and second magnetic layer 840.Moreover, the time to switch between stable states may be reduced andthe reliability of switching of magnetic device 800 may be relativelygreater than prior art devices which do not include non-collinearlycoupled structure 810.

When third magnetic layer 870 is in its first state, the resistanceacross body 812 (as can be measured by circuit 895) may have a firstvalue. When third magnetic layer 870 is in its second state, theresistance across body 812 (as can be measured by circuit 895) may havea second value, different from the first value. Therefore, bydetermining the resistance across body 812 (as can be measured bycircuit 895), it is possible to determine the state of third magneticlayer 870. Information such as a bit can therefore be stored on magneticdevice 800. For example, the first state of third magnetic layer 870(and its associated first value of resistance) could correspond to a “0”bit and the second state of third magnetic layer 870 (and its associatedsecond value of resistance) could correspond to a “1” bit.

FIG. 32B is a schematic diagram of a magnetic device 900 according toone embodiment of the invention. Magnetic device 900 may be employed as(or as part of), for example, a magnetic memory device, a magneticsensor device, an oscillator device, a diode, a microwave generator oran energy harvesting device.

Magnetic device 900 is substantially similar to magnetic device 800except as described below. Moreover, magnetic device 900 may be employedin the same way that magnetic device 800 may be employed as describedabove and magnetic device 900 may have the same (or some of the same)advantages that magnetic device 800 has as described above in additionto those described below. Magnetic device 900 comprises a first magneticstructure 910 similar to magnetic structure 810, first, second and thirdmagnetic layers 930, 940, 970 having first, second and thirdmagnetization directions 932, 942, 972 similar to first, second andthird magnetic layers 830, 840, 870 having first, second and thirdmagnetization directions 832, 842, 872, a first coupling layer 920similar to coupling layer 820, a first magnetoresistive layer 960similar to magnetoresistive layer 860 and a circuit 995 similar tocircuit 895.

Magnetic device 900 also comprises a second magnetic structure 915comprising fourth magnetic layer 980 having fourth magnetizationdirection 982 and fifth magnetic layer 990 having fifth magnetizationdirection 992 separated by a second coupling layer 925. Fourth magneticlayer 980 is spaced apart from third magnetic layer 970 by secondmagnetoresistive layer 965. Together, first, second, third, fourth andfifth magnetic layers 930, 940, 970, 980, 990, first coupling layer 920,second coupling layer 925, first magnetoresistive layer 960 and secondmagnetoresistive layer 965 may be referred to as body 912.

First and second magnetic layers 930, 940 may be non-collinearly coupledsuch that first magnetization direction 932 is oriented at anon-collinear angle with respect to second magnetization direction 942.First magnetization direction 932 is oriented in either the positive Zdirection or the negative Z direction (e.g. orthogonal to the XY plane).First magnetization direction 932 is fixed. Second magnetizationdirection 942 is oriented at least partially in the Z direction and atleast partially in one or both of the X and Y directions. It should beunderstood that in some embodiments second magnetization direction 942may rotate (or have any relative orientation) about a Z direction axiswhile remaining fixed to first magnetization direction 932 at thenon-collinear angle.

Fourth and fifth magnetic layers 980, 990 may also be non-collinearlycoupled such that fourth magnetization direction 982 is oriented at anon-collinear angle with respect to fifth magnetization direction 992.Fifth magnetization direction 992 is oriented in either the positive Zdirection or the negative Z direction (e.g. orthogonal to the XY plane).Fifth magnetization 992 direction is fixed. Fourth magnetizationdirection 982 is oriented at least partially in the Z direction and atleast partially in one or both of the X and Y directions. It should beunderstood that in some embodiments fourth magnetization direction 982may rotate (or have any relative orientation) about a Z direction axiswhile remaining fixed to fifth magnetization direction 992 at thenon-collinear angle. The non-collinear coupling angle between fourth andfifth magnetic layers 980, 990 may be different from the non-collinearcoupling angle between first and second magnetic layers 930, 940.

Any suitable apparatus or method may be employed to fix first and fifthmagnetization directions 932, 992. For example, the materials of firstand fifth magnetic layers 930, 990 may be chosen such that magnetizationdirections 932, 992 are fixed. Alternatively, additional magnetic layersmay be ferromagnetically coupled or coupled by a coupling layer (e.g.ferromagnetically, antiferromagnetically or non-collinearly coupled) tofirst and fifth magnetic layers 930, 990 to thereby fix first and fifthmagnetization directions 932, 992.

Third magnetization direction 972 is free relative to first and secondmagnetization directions 932, 942 and fourth and fifth magnetizationdirections 982, 992. Specifically, third magnetization direction 972 isfree to change between a first state wherein third magnetizationdirection 972 is oriented generally in the positive Z direction and asecond state wherein third magnetization direction 972 is orientedgenerally in the negative Z direction.

When third magnetic layer 970 is in its first state, the resistanceacross body 912 (as can be measured by circuit 995) may have a firstvalue. When third magnetic layer 970 is in its second state, theresistance across body 912 (as can be measured by circuit 995) may havea second value, different from the first value. Therefore, bydetermining the resistance across body 912 (as can be measured bycircuit 995), it is possible to determine the state of third magneticlayer 970. Information such as a bit can therefore be stored on magneticdevice 900. For example, the first state of third magnetic layer 970(and its associated first value of resistance) could correspond to a “0”bit and the second state of third magnetic layer 970 (and its associatedsecond value of resistance) could correspond to a “1” bit.

As compared to magnetic device 800, the difference between theresistance of body 912 when third magnetic layer 970 is in its firststate as compared to the resistance of body 912 when third magneticlayer 970 is in its second state may be higher than the differencebetween the resistance of body 812 when third magnetic layer 870 is inits first state as compared to the resistance of body 812 when thirdmagnetic layer 870 is in its second state. This relatively greaterresistance difference (of device 900 relative to device 800) may be aresult of constructive interference of torque of the polarized currentthat has passed through second magnetic layer 940 (or fourth magneticlayer 980) and torque of the current that is reflected by fourthmagnetic layer 980 (or by second magnetic layer 940), thereby resultingin an increase in net torque on third magnetization direction 972.Further explanation of such constructive interference is described belowin relation to magnetic device 3100.

Third magnetization direction 972 of third magnetic layer 970 can becaused to change between its first and second states by spin torquetransfer (e.g. applying a current through circuit 995). By passing thecurrent through second magnetic layer 940 (or through fourth magneticlayer 980), the electric current is polarized in a first direction. Bypassing the polarized current through third magnetic layer 970, thepolarized current causes the third magnetic layer 870 to change from itsfirst stable state to its second stable state (or vice versa). Theamount of current for changing third magnetic layer 970 between itsstable states may depend on the angular difference between thirdmagnetization direction 972 and second magnetization direction 942and/or the angular difference between third magnetization direction 972and fourth magnetization direction 982 depending on which way current ispassed through body 912. If current is passed first through firstmagnetic layer 932, the current may be reduced by changing the angulardifference between the third magnetization direction 972 and secondmagnetization direction 942. If current is passed first through fifthmagnetic layer 992, the current may be reduced by changing the angulardifference between third magnetization direction 972 and fourthmagnetization direction 982. Changing the angular difference betweenthird magnetization direction 972 and second magnetization direction 942and/or changing the angular difference between third magnetizationdirection 972 and fourth magnetization direction 982 may be accomplishedwith non-collinear coupling (e.g. by employing magnetic structure 10and/or coupling layer 20, as described herein) between first and secondmagnetic layers 930, 940 and/or between fourth and fifth magnetic layers980, 990, respectively. In some embodiments, by changing the angulardifference between third magnetization direction 972 and secondmagnetization direction 942 and/or changing the angular differencebetween third magnetization direction 972 and fourth magnetizationdirection 982, switching time may be increased and resistance changesbetween states may be decreased.

By coupling first and second magnetization directions 932, 942 at anon-collinear angle and by coupling fourth and fifth magnetizationdirections 982, 992 at a non-collinear angle, the amount of current tochange third magnetic layer 970 between its first and second states maybe reduced considerably as compared to prior art devices which useferromagnetic coupling and/or antiferromagnetic coupling between firstmagnetic layer 930 and second magnetic layer 940 and/or between fourthmagnetic layer 980 and fifth magnetic layer 980. Moreover, the time toswitch between stable states may be reduced and the reliability ofswitching of magnetic device 900 may be relatively greater when comparedto prior art devices which do not use non-collinearly coupling.

In FIGS. 32A and 32B, first magnetization directions 832, 932 aredepicted as being out-of-plane (e.g. at least a component of each offirst magnetization directions 832, 932 extends out of the XY-plane).This is not mandatory. First magnetization directions 832, 932 may bein-plane (e.g. first magnetization directions 832, 932 may havesubstantially no Z-direction components).

FIGS. 33A and 33B are schematic diagrams of magnetic devices 1000 and1100, which are respectively substantially similar to magnetic devices800 and 900, except as described below. Magnetic devices 1000, 1100 mayeach be employed as (or as part of), for example, a magnetic memorydevice, a magnetic sensor device, an oscillator device, a diode, amicrowave generator or an energy harvesting device. Moreover, magneticdevices 1000, 1100 may be employed in the same way that magnetic devices800, 900 respectively may be employed as described above and magneticdevices 1000, 1100 have the same advantages that magnetic devices 800,900 respectively have as described above in addition to those describedbelow.

Magnetic device 1000 comprises a magnetic structure 1010 similar tomagnetic structure 810, first, second and third magnetic layers 1030,1040, 1070 having first, second and third magnetization directions 1032,1042, 1072 similar to first, second and third magnetic layers 830, 840,870 having first, second and third magnetization directions 832, 842,872, a first coupling layer 1020 similar to coupling layer 820, amagnetoresistive layer 1060 similar to magnetoresistive layer 860 and acircuit 1095 similar to circuit 895. Together, first, second and thirdmagnetic layers 1030, 1040, 1070, first coupling layer 1020, andmagnetoresistive layer 1060 may be referred to as body 1012.

In the depicted embodiment, magnetic device 1000 differs from magneticdevice 800 in that first magnetization direction 1032 is in-plane (e.g.first magnetization direction 1032 does not have a Z directioncomponent) and is oriented in the X direction as opposed to firstmagnetization direction 832 which is out-of-plane (e.g. firstmagnetization direction 832 has a Z direction component and extends outof the XY-plane). It should be understood, that first magnetizationdirection 1032 could also be in-plane and oriented in the Y direction ora combination of the X and Y directions.

In some embodiments, second magnetic layer 1040 of magnetic device 1000(or all of magnetic device 1000) has an XY-plane cross-section that iselongated in the X direction. Referring back to the discussion of FIG.3B, the elongated X-direction of the XY-plane cross-section may urge orlimit the orientation of second magnetization direction 1042 to be inthe XZ-plane. Therefore, in such embodiments, to maintain thenon-collinear coupling angle between first and second magnetizationdirections 1032, 1042, second magnetization direction 1042 is fixed in asingle orientation in the XZ-plane. By limiting second magnetizationdirection 1042 to a single orientation, the number of pinning layers (orother pinning features) may be reduced in such embodiments, compared toembodiments having non-elongated X-Y plane cross-sections.

Magnetic device 1100 comprises a first and second magnetic structures1110, 1115 similar to magnetic structures 910, 915 first, second, third,fourth and fifth magnetic layers 1130, 1140, 1170, 1180, 1190 havingfirst, second, third, fourth and fifth magnetization directions 1132,1142, 1172, 1182, 1192 similar to first, second, third, fourth and fifthmagnetic layers 930, 940, 970, 980, 990 having first, second, third,fourth and fifth magnetization directions 932, 942, 972, 982, 992, firstand second coupling layer 1120, 1125 similar to coupling layers 920,925, first and second magnetoresistive layers 1160, 1165 similar tomagnetoresistive layers 960, 965 and a circuit 1195 similar to circuit995. Together, first, second, third, fourth and fifth magnetic layers1130, 1140, 1170, 1180, 1190, first coupling layer 1120, second couplinglayer 1125, first magnetoresistive layer 1160 and secondmagnetoresistive layer 1165 may be referred to as body 1112.

In the depicted embodiment, magnetic device 1100 differs from magneticdevice 900 in that first and fifth magnetization directions 1032, 1092are in-plane (e.g. first and fifth magnetization directions 1032, 1092do not have Z direction components) and are oriented in the X directionas opposed to first and fifth magnetization direction 932, 992 which areout-of-plane (e.g. first and fifth magnetization directions 932, 992have Z direction components and extend out of the XY-plane).

In some embodiments, second and/or fourth magnetic layers 1140, 1180 ofmagnetic device 1100 (or all of magnetic device 1100) each have anXY-plane cross-section that is elongated in the X direction. Referringback to the discussion of FIG. 3B, the elongated X-dimension of theXY-plane cross-section may urge or limit the orientation of secondmagnetization direction 1142 and/or fourth magnetization direction 1182to be in the XZ-plane. Therefore, in such embodiments, to maintain thenon-collinear coupling angle between first and second magnetizationdirections 1132, 1142 and/or fourth and fifth magnetization directions1182, 1192, second and/or fourth magnetization directions 1142, 1182 arefixed in a single orientation in the XZ-plane. By limiting second and/orfourth magnetization directions 1142, 1182 to a single orientation, thenumber of pinning layers (or other pinning features) may be reduced insuch embodiments, compared to embodiments having non-elongated X-Y planecross-sections.

While FIGS. 33A and 33B depict first magnetization directions 1032, 1132as extending in the X direction and having no Z direction component, itmay also be possible to fix second magnetization directions 1042, 1142and fourth magnetization direction 1182 in a single orientation even iffirst magnetization directions 1032, 1132 and fifth magnetizationdirection 1192 have non-zero Z direction components, non-zero Xdirection components and/or non-zero Y direction components. Forexample, FIGS. 34A and 34B depict magnetic devices 1200, 1300substantially similar to magnetic devices 1000, 1100 respectively, inwhich first magnetization directions 1232, 1332 of magnetic devices1200, 1300 have non-zero X direction components and non-zero Z directioncomponents. Magnetic devices 1200, 1300 may be substantially similar tomagnetic devices 1000, 1100 respectively, except as described below.Moreover, magnetic devices 1200, 1300 may be employed in the same waythat magnetic devices 1000, 1100 respectively may be employed asdescribed above and magnetic devices 1200, 1300 have the same advantagesthat magnetic devices 1000, 1100 have as described above in addition tothose described below.

Magnetic device 1200 comprises a magnetic structure 1210 similar tomagnetic structure 1010, first, second and third magnetic layers 1230,1240, 1270 having first, second and third magnetization directions 1232,1242, 1272 similar to first, second and third magnetic layers 1030,1040, 1070 having first, second and third magnetization directions 1032,1042, 1072, a first coupling layer 1220 similar to coupling layer 1020,a magnetoresistive layer 1260 similar to magnetoresistive layer 1060 anda circuit 1295 similar to circuit 1095. Together, first, second andthird magnetic layers 1230, 1240, 1270, first coupling layer 1220, andmagnetoresistive layer 1260 may be referred to as body 1212.

In the depicted embodiment, magnetic device 1200 differs from magneticdevice 1000 in that first magnetization direction 1232 has a non-zero Zdirection component as opposed to first magnetization direction 1032which is in-plane (e.g. first magnetization direction 1032 has no Zdirection component).

In some embodiments, second magnetic layer 1240 of magnetic device 1200(or all of magnetic device 1200) has an XY-plane cross-section that iselongated in the X direction. Referring back to the discussion of FIG.3B, the elongated XY-plane cross-section may urge or limit theorientation of second magnetization direction 1242 to be in theXZ-plane. Therefore, in such embodiments, to maintain the non-collinearcoupling angle between first and second magnetization directions 1232,1242, second magnetization direction 1242 is fixed in a singleorientation in the XZ-plane. By limiting second magnetization direction1242 to a single orientation, the number of pinning layers (or otherpinning features) may be reduced in such embodiments, compared toembodiments having non-elongated X-Y plane cross-sections.

Magnetic device 1300 comprises a first and second magnetic structures1310, 1315 similar to magnetic structures 1110, 1115 first, second,third, fourth and fifth magnetic layers 1330, 1340, 1370, 1380, 1390having first, second, third, fourth and fifth magnetization directions1332, 1342, 1372, 1382, 1392 similar to first, second, third, fourth andfifth magnetic layers 1130, 1140, 1170, 1180, 1190 having first, second,third, fourth and fifth magnetization directions 1132, 1142, 1172, 1182,1192, first and second coupling layer 1320, 1325 similar to couplinglayers 1120, 1125, first and second magnetoresistive layers 1360, 1365similar to magnetoresistive layers 1160, 1165 and a circuit 1395 similarto circuit 1195. Together, first, second, third, fourth and fifthmagnetic layers 1330, 1340, 1370, 1380, 1390, first coupling layer 1320,second coupling layer 1325, first magnetoresistive layer 1360 and secondmagnetoresistive layer 1365 may be referred to as body 1312.

In the depicted embodiment, magnetic device 1300 differs from magneticdevice 1100 in that first and fifth magnetization directions 1332, 1392each have a non-zero Z direction component as opposed to first and fifthmagnetization direction 1132, 1192 which are have substantially noZ-direction components.

In some embodiments, second and/or fourth magnetic layers 1340, 1380 ofmagnetic device 1300 (or all of magnetic device 1300) each have anXY-plane cross-section that is elongated in the X direction. Referringback to the discussion of FIG. 3B, the elongated XY-plane cross-sectionmay urge or limit the orientation of second magnetization direction 1342and/or fourth magnetization direction 1382 to be in the XZ-plane.Therefore, in such embodiments, to maintain the non-collinear couplingangle between first and second magnetization directions 1332, 1342and/or fourth and fifth magnetization directions 1382, 1392, second and/or fourth magnetization directions 1342, 1382 are fixed in a singleorientation in the XZ-plane. By limiting second and/or fourthmagnetization directions 1342, 1382 to a single orientation, the numberof pinning layers (or other pinning features) may be reduced in suchembodiments, compared to embodiments having non-elongated X-Y planecross-sections.

First magnetic layers 1230, 1330 and fifth magnetic layer 1390 ofmagnetic devices 1200, 1300 may be orthogonally, non-collinearly coupledto second magnetic layers 1240, 1340, and fourth magnetic layer 1380respectively, although this is not necessary.

While the free layers in magnetic devices 800, 900, 1000, 1100, 1200,1300 discussed above have been depicted and discussed as having thirdmagnetization directions 872, 972, 1072, 1172, 1272, 1372 oriented inthe Z direction without having any X or Y direction components, this isnot mandatory. Third magnetization directions 872, 972, 1072, 1172,1272, 1372 may be oriented substantially in the X direction (e.g. if theXY plane cross-sections of magnetic devices 800, 900, 1000, 1100, 1200,1300 (or at least free third magnetic layers 870, 970, 1070, 1170, 1270,1370) are elongated in the X direction). Similarly, the thirdmagnetization directions 872, 972, 1072, 1172, 1272, 1372 may beoriented in the Y direction (e.g. if the XY plane cross-sections ofmagnetic devices 800, 900, 1000, 1100, 1200, 1300 (or at least thirdmagnetic layers 870, 970, 1070, 1170, 1270, 1370) are elongated in the Ydirection).

FIGS. 35A, 35B, 36A, 36B, 37A and 37B are schematic diagrams of magneticdevices 1400, 1500, 1600, 1700, 1800, 1900 respectively. Magneticdevices 1400, 1500, 1600, 1700, 1800, 1900 are substantially similar tomagnetic devices 800, 900, 1000, 1100, 1200, 1300 respectively, exceptthat the XY plane cross-sections of free third magnetic layers 1470,1570, 1670, 1770, 1870, 1970 are elongated in the X direction and thecorresponding third magnetization directions 1472, 1572, 1672, 1772,1872, 1972 are oriented in the XY-plane. Moreover, magnetic devices1400, 1500, 1600, 1700, 1800, 1900 may be employed in the same way thatmagnetic devices 800, 900, 1000, 1100, 1200, 1300 respectively may beemployed as described above and magnetic devices 1400, 1500, 1600, 1700,1800, 1900 have the same advantages that magnetic devices 800, 900,1000, 1100, 1200, 1300 have as described above in addition to thosedescribed below.

Magnetic device 1400 comprises a magnetic structure 1410 similar tomagnetic structure 810, first, second and third magnetic layers 1430,1440, 1470 having first, second and third magnetization directions 1432,1442, 1472 similar to first, second and third magnetic layers 830, 840,870 having first, second and third magnetization directions 832, 842,872, a first coupling layer 1420 similar to coupling layer 820, amagnetoresistive layer 1460 similar to magnetoresistive layer 860 and acircuit 1495 similar to circuit 895. Together, first, second and thirdmagnetic layers 1430, 1440, 1470, first coupling layer 1420, andmagnetoresistive layer 1460 may be referred to as body 1412.

Magnetic device 1500 comprises first and second magnetic structures1510, 1515 similar to magnetic structures 910, 915 first, second, third,fourth and fifth magnetic layers 1530, 1540, 1570, 1580, 1590 havingfirst, second, third, fourth and fifth magnetization directions 1532,1542, 1572, 1582, 1592 similar to first, second, third, fourth and fifthmagnetic layers 930, 940, 970, 980, 990 having first, second, third,fourth and fifth magnetization directions 932, 942, 972, 982, 992, firstand second coupling layer 1520, 1525 similar to coupling layers 920,925, first and second magnetoresistive layers 1560, 1565 similar tomagnetoresistive layers 960, 965 and a circuit 1595 similar to circuit995. Together, first, second, third, fourth and fifth magnetic layers1530, 1540, 1570, 1580, 1590, first coupling layer 1520, second couplinglayer 1525, first magnetoresistive layer 1560 and secondmagnetoresistive layer 1565 may be referred to as body 1512.

Magnetic device 1600 comprises a magnetic structure 1610 similar tomagnetic structure 1010, first, second and third magnetic layers 1630,1640, 1670 having first, second and third magnetization directions 1632,1642, 1672 similar to first, second and third magnetic layers 1030,1040, 1070 having first, second and third magnetization directions 1032,1042, 1072, a first coupling layer 1620 similar to coupling layer 1020,a magnetoresistive layer 1660 similar to magnetoresistive layer 1060 anda circuit 1695 similar to circuit 1095. Together, first, second andthird magnetic layers 1630, 1640, 1670, first coupling layer 1620, andmagnetoresistive layer 1660 may be referred to as body 1612.

Magnetic device 1700 comprises a first and second magnetic structures1710, 1715 similar to magnetic structures 1110, 1115 first, second,third, fourth and fifth magnetic layers 1730, 1740, 1770, 1780, 1790having first, second, third, fourth and fifth magnetization directions1732, 1742, 1772, 1782, 1792 similar to first, second, third, fourth andfifth magnetic layers 1130, 1140, 1170, 1180, 1190 having first, second,third, fourth and fifth magnetization directions 1132, 1142, 1172, 1182,1192, first and second coupling layer 1720, 1725 similar to couplinglayers 1120, 1125, first and second magnetoresistive layers 1760, 1765similar to magnetoresistive layers 1160, 1165 and a circuit 1795 similarto circuit 1195. Together, first, second, third, fourth and fifthmagnetic layers 1730, 1740, 1770, 1780, 1790, first coupling layer 1720,second coupling layer 1725, first magnetoresistive layer 1760 and secondmagnetoresistive layer 1765 may be referred to as body 1712.

Magnetic device 1800 comprises a magnetic structure 1810 similar tomagnetic structure 1210, first, second and third magnetic layers 1830,1840, 1870 having first, second and third magnetization directions 1832,1842, 1872 similar to first, second and third magnetic layers 1230,1240, 1270 having first, second and third magnetization directions 1232,1242, 1272, a first coupling layer 1820 similar to coupling layer 1220,a magnetoresistive layer 1860 similar to magnetoresistive layer 1260 anda circuit 1895 similar to circuit 1295. Together, first, second andthird magnetic layers 1830, 1840, 1870, first coupling layer 1820, andmagnetoresistive layer 1860 may be referred to as body 1812.

Magnetic device 1900 comprises a first and second magnetic structures1910, 1915 similar to magnetic structures 1310, 1315 first, second,third, fourth and fifth magnetic layers 1930, 1940, 1970, 1980, 1990having first, second, third, fourth and fifth magnetization directions1932, 1942, 1972, 1982, 1992 similar to first, second, third, fourth andfifth magnetic layers 1330, 1340, 1370, 1380, 1390 having first, second,third, fourth and fifth magnetization directions 1332, 1342, 1372, 1382,1392, first and second coupling layer 1920, 1925 similar to couplinglayers 1320, 1325, first and second magnetoresistive layers 1960, 1965similar to magnetoresistive layers 1360, 1365 and a circuit 1995 similarto circuit 1395. Together, first, second, third, fourth and fifthmagnetic layers 1930, 1940, 1970, 1980, 1990, first coupling layer 1920,second coupling layer 1925, first magnetoresistive layer 1960 and secondmagnetoresistive layer 1965 may be referred to as body 1912.

If the XY plane cross-sections of free third magnetic layers 1470 1570,1670, 1770, 1870, 1970 are elongated in the X direction andcorresponding the third magnetization directions 1472, 1572, 1672, 1772,1872, 1972 are oriented in the X direction, then third magnetizationdirections 1472, 1572, 1672, 1772, 1872, 1972 may have two stable states(as opposed to infinite stable states if the X and Y directiondimensions are approximately equal). The first stable state may beoriented in the positive X direction and the second stable state may beoriented in the negative X direction. Otherwise, magnetic devices 1400,1500, 1600, 1700, 1800, 1900 can be employed and function insubstantially the same way as magnetic devices 800, 900, 1000, 1100,1200, 1300 discussed above.

FIG. 38A is a schematic diagram of a magnetic device 2000 according to aparticular embodiment. Magnetic device 2000 is substantially similar tomagnetic device 400 except in that while the X direction dimension andthe Y direction dimension of magnetic device 400 are substantially equalto one another (see FIG. 30A), the X direction dimension of magneticdevice 2000 may be elongated as compared to the Y direction dimension ofmagnetic device 2000. Magnetic device 2000 may be employed in the sameway that magnetic device 400 may be employed as described above inaddition to as described below and magnetic device 2000 may have thesame (or some of the same) advantages that magnetic device 400 has asdescribed above in addition to those described below. Magnetic device2000 comprises a magnetic structure 2010 similar to magnetic structure410, first, second and third magnetic layers 2030, 2040, 2070 havingfirst, second and third magnetization directions 2032, 2042, 2072similar to first, second and third magnetic layers 430, 440, 470, afirst coupling layer 2020 similar to coupling layer 420, amagnetoresistive layer 2060 similar to magnetoresistive layer 460, abody 2012 similar to body 412 and a circuit 2095 similar to circuit 495.

Like first, second and third magnetization directions 432, 442, 472,first and third magnetization directions 2032, 2072 are fixed whilesecond magnetization direction 2042 is free. However, while secondmagnetization direction 442 of magnetic device 400 is allowed to rotateabout the Z direction axis while being non-collinearly coupled to firstmagnetization direction 432, second magnetization direction 2042 isbiased not to rotate about the Z direction axis due to the elongation ofsecond magnetic layer 2040 in the X direction (as compared to the Ydirection). Instead, second magnetization direction 2042 has two stablestates in the XZ-plane: a first state in which second magnetizationdirection 2042 extends in the positive Z direction and the positive Xdirection and a second state in which second magnetization direction2042 extends in the positive Z direction and the negative X direction.Alternatively, second magnetization direction 2042 could have two stablestates in the XZ-plane: a first state in which second magnetizationdirection 2042 extends in the negative Z direction and the positive Xdirection and a second state in which second magnetization direction2042 extends in the negative Z direction and the negative X direction.

Second magnetization direction 2042 of second magnetic layer 2040 can becaused to change between its first and second states by spin torquetransfer (e.g. applying a current through circuit 2095). By passing thecurrent through third magnetic layer 2070, the electric current ispolarized. By passing the polarized current through second magneticlayer 2040, the polarized current may cause the second magnetic layer2040 to change from its first stable state to its second stable state(or vice versa). The amount of current for changing second magneticlayer 2040 between its two states may depend on the angular differencebetween first magnetization direction 2032 and second magnetizationdirection 2042. The current may be reduced by changing the angulardifference between the third magnetization direction 2072 and secondmagnetization direction 2042. Changing the angular difference betweenthird magnetization direction 2072 and second magnetization direction2042 may be accomplished with non-collinear coupling (e.g. by employingmagnetic structure 10 and/or coupling layer 20, as described herein)between first and second magnetic layers 2030, 2040.

FIG. 38B is a schematic diagram of a magnetic device 2100 according to aparticular embodiment. Magnetic device 2100 is substantially similar tomagnetic device 500 except in that while the X direction dimension andthe Y direction dimension of magnetic device 500 are substantially equalto one another (see FIG. 30B), the X direction dimension of magneticdevice 2100 may be elongated as compared to the Y direction dimension ofmagnetic device 2100. Moreover, magnetic device 2100 may be employed inthe same way that magnetic device 500 may be employed as described aboveand magnetic device 2100 may have the same (or some of the same)advantages that magnetic device 500 has as described above in additionto those described below. Magnetic device 2100 comprises a magneticstructure 2110 similar to magnetic structure 510, first, second andthird magnetic layers 2130, 2140, 2170 having first, second and thirdmagnetization directions 2132, 2142, 2172 similar to first, second andthird magnetic layers 530, 540, 570, a first coupling layer 2120 similarto coupling layer 520, a magnetoresistive layer 2160 similar tomagnetoresistive layer 560, a body 2112 similar to body 512 and acircuit 2195 similar to circuit 595. First and second magnetic layers2130, 2140 may be coupled at an orthogonal, non-collinear angle,although this is not necessary.

Like first, second and third magnetization directions 532, 542, 572,third magnetization direction 2172 is fixed while first and secondmagnetization directions 2132, 2142 are free. However, while first andsecond magnetization directions 532, 542 of magnetic device 500 areallowed to rotate about the Z direction axis while being non-collinearlycoupled, first and second magnetization directions 2132, 2142 are biasednot to rotate about the Z direction axis due to the elongation of secondmagnetic layer 2140 in the X direction (as compared to the Y direction).Instead, first and second magnetization directions 2132, 2142 each havetwo stable states in the XZ-plane. First magnetization direction 2132has a first state in which first magnetization direction extends in thenegative Z direction and the positive X direction and a second state inwhich first magnetization direction extends in the negative Z directionand the negative X direction. Second magnetization direction 2142 has afirst state in which second magnetization direction 2142 extends in thepositive Z direction and the positive X direction and a second state inwhich second magnetization direction 2142 extends in the positive Zdirection and the negative X direction.

First and second magnetization directions 2132, 2142 can be caused tochange between their first and second states by spin torque transfer(e.g. applying a current through circuit 2195). By passing the currentthrough third magnetic layer 2170, the electric current is polarized. Bypassing the polarized current through second magnetic layer 2140, thepolarized current may cause the first and second magnetic layers 2130,2140 to change between stable states. The amount of current for changingfirst and second magnetic layers 2130, 2140 between their respective maydepend on the angular difference between third magnetization direction2172 and second magnetization direction 2142. The current may be reducedby changing the angular difference between the third magnetizationdirection 2172 and second magnetization direction 2142. Changing theangular difference between third magnetization direction 2172 and secondmagnetization direction 2142 may be accomplished with non-collinearcoupling (e.g. by employing magnetic structure 10 and/or coupling layer21, as described herein) between first and second magnetic layers 2130,2140.

In some embodiments, the X direction dimension of magnetic device 2100is approximately equal to the Y direction dimension of magnetic device2100 and each of first and second magnetization directions 2132, 2142may rotate (or precess) about a Z direction axis.

FIG. 38C is a schematic diagram of a magnetic device 2200 according to aparticular embodiment. Magnetic device 2200 is substantially similar tomagnetic device 2100 except as described below. Moreover, magneticdevice 2200 may be employed in the same way that magnetic device 2100may be employed as described above and magnetic device 2200 may have thesame (or some of the same) advantages that magnetic device 2100 has asdescribed above in addition to those described below.

Magnetic device 2200 comprises a magnetic structure 2210 similar tomagnetic structure 2110, first, second and third magnetic layers 2230,2240, 2270 having first, second and third magnetization directions 2232,2242, 2272 similar to first, second and third magnetic layers 2130,2140, 2170, a first coupling layer 2220 similar to coupling layer 2120,a first magnetoresistive layer 2260 similar to magnetoresistive layer2160, and a circuit 2295 similar to circuit 2195. Magnetic device 2200also comprises a second magnetoresistive layer 2265 spaced between firstmagnetic layer 2230 and a fourth magnetic layer 2280 having a fourthmagnetization direction 2282. Together, first, second, third and fourthmagnetic layers 2230, 2240, 2270, 2280, first and secondmagnetoresistive layers 2260, 2265 and coupling layer 2220 may bereferred to as body 2212. Like magnetic device 2100, both of first andsecond magnetization directions 2232, 2242 are free and thirdmagnetization direction 2272 is fixed. First and second magnetic layers2232, 2242 may in practice, in combination with coupling layer 2220, actor be treated as one free magnetic layer. Fourth magnetization direction2282 may also be fixed. The addition of second magnetoresistive layer2265 and fourth magnetic layer 2280 may serve to increase the resistivechange across body 2212 of magnetic device 2200 when first and secondmagnetic layers 2230, 2240 change states, reduce switching time and/orreduce current for switching relative to device 2100.

FIG. 38D is a schematic diagram of a magnetic device 2300 according to aparticular embodiment. Magnetic device 2300 may be substantially similarto magnetic device 2200 except as described below. Moreover, magneticdevice 2300 may be employed in the same way that magnetic device 2200may be employed as described above and magnetic device 2300 may have thesame (or some of the same) advantages that magnetic device 2200 has asdescribed above in addition to those described below.

Magnetic device 2300 comprises a magnetic structure 2310 similar tomagnetic structure 2210, first, second, third and fourth magnetic layers2330, 2340, 2370, 2380 having first, second, third and fourthmagnetization directions 2332, 2342, 2372, 2282 similar to first,second, third and fourth magnetic layers 2230, 2240, 2270, 2280 a firstcoupling layer 2320 similar to coupling layer 2220, first and secondmagnetoresistive layers 2360, 2365 similar to magnetoresistive layers2260, 2265 and a circuit 2395 similar to circuit 2295. Together, first,second, third and fourth magnetic layers 2330, 2340, 2370, 2380, firstand second magnetoresistive layers 2360, 2365 and coupling layer 2320may be referred to as body 2312. Like magnetic device 2200, both offirst and second magnetization directions 2332, 2342 are free and thirdand fourth magnetization directions 2372, 2382 are fixed.

Magnetic device 2300 differs from magnetic device 2200 in that firstmagnetization direction 2332 is in-plane (e.g. first magnetizationdirection 2332 has no Z direction component) while first magnetizationdirection 2232 is out-of-plane (e.g. first magnetization direction 2232has a Z direction component).

In some embodiments, the X direction dimension of magnetic device 2300is approximately equal to the Y direction dimension of magnetic device2300 and each of first and second magnetization directions 2332, 2342may rotate about a Z direction axis. In other embodiments, the Xdirection dimension of magnetic device 2300 is elongated with respect tothe Y direction dimension of magnetic device 2300 and each of first andsecond magnetization directions 2332, 2342 may flip from a first statewhere their respective X direction components are oriented in thepositive X direction and a second state where their respective Xdirection components are oriented in a negative X direction.

Since first magnetization direction 2332 is in-plane, the changes inresistance across second magnetoresistive layer 2365 are increased ascompared to changes in resistance across magnetoresistive layer 2265.However, more torque may be required to change states of firstmagnetization direction 2332 which may in turn lead to increasedswitching time. Accordingly, it follows that for embodiments where it isbeneficial to have greater changes in resistance across body 2312, it isdesirable for first and/or second magnetization directions 2332, 2342 tobe in-plane whereas for where it is beneficial to have faster switchingtimes and/or reduced switching current/torque, it is desirable for firstand/or second magnetization directions 2332, 2342 to be out-of-plane(e.g. to have Z direction components). By having one of first and/orsecond magnetization directions 2332, 2342 be in-plane and one of firstand/or second magnetization directions 2332, 2342 have a Z directioncomponent, it may be possible to balance between a desire for reducedswitching current/torque (and/or faster switching times) and increasedchanges in resistance between states.

FIG. 39A is a schematic diagram of a magnetic device 2400 according to aparticular embodiment. Magnetic device 2400 may be substantially similarto magnetic device 2000 except as described below. Moreover, magneticdevice 2400 may be employed in the same way that magnetic device 2000may be employed as described above and magnetic device 2400 may have thesame (or some of the same) advantages that magnetic device 2000 has asdescribed above in addition to those described below. Magnetic device2400 comprises a magnetic structure 2410 similar to magnetic structure2010, first, second and third magnetic layers 2430, 2440, 2470 havingfirst, second and third magnetization directions 2432, 2442, 2472similar to first, second and third magnetic layers 2030, 2040, 2070, afirst coupling layer 2420 similar to coupling layer 2020, amagnetoresistive layer 2460 similar to magnetoresistive layer 2060, abody 2412 similar to body 2012 and a circuit 2495 similar to circuit2095.

Like first, second and third magnetization directions 2032, 2042, 2072,first and third magnetization directions 2432, 2472 are fixed whilesecond magnetization direction 2442 is free. However, while secondmagnetization direction 2042 of magnetic device 2000 has first andsecond states that differ between their positive and negative Xdirection orientations (while their Z direction orientations remainconstant), second magnetization direction 2442 has first and secondstates that remain constant in their X direction orientation but changein their Z direction orientation. In other words, second magnetizationdirection 2042 may rotate or switch about a Z direction axis to changestates, whereas second magnetization direction 2442 may rotate or switchabout an X direction axis to change states.

Third magnetization direction 2472 is depicted as being oriented in thepositive Z direction. This is not mandatory. Third magnetizationdirection 2472 could be oriented in the negative Z direction. Moreover,third magnetization direction 2472 could have an X direction component(and/or a Y direction component). By orienting third magnetizationdirection 2472 without a substantial X direction component, the changesin resistance across body 2412 are greater as second magnetizationdirection 2442 changes states as compared to if third magnetizationdirection 2472 were to have a substantial X direction component.

Second magnetization direction 2442 of second magnetic layer 2440 can becaused to change between its first and second states by spin torquetransfer (e.g. applying a current through circuit 2495). By passing thecurrent through third magnetic layer 2470, the electric current ispolarized. By passing the polarized current through second magneticlayer 2440, the polarized current may cause the second magnetic layer2440 to change from its first stable state to its second stable state(or vice versa).

The amount of current for changing states of second magnetic layer 2440may depend on the angular difference between third magnetizationdirection 2472 and second magnetization direction 2442. The current maybe reduced by changing the angular difference between the thirdmagnetization direction 2472 and second magnetization direction 2442.Changing the angular difference between third magnetization direction2472 and second magnetization direction 2442 may be accomplished withnon-collinear coupling (e.g. by employing magnetic structure 10 and/orcoupling layer 24, as described herein) between first and secondmagnetic layers 2430, 2440.

FIG. 39B is a schematic diagram of a magnetic device 2500 according to aparticular embodiment. Magnetic device 2500 may be substantially similarto magnetic device 2400 except as described below. Moreover, magneticdevice 2500 may be employed in the same way that magnetic device 2400may be employed as described above and magnetic device 2500 may have thesame (or some of the same) advantages that magnetic device 2400 has asdescribed above in addition to those described below. Magnetic device2500 comprises a magnetic structure 2510 similar to magnetic structure2410, first, second and third magnetic layers 2530, 2540, 2570 havingfirst, second and third magnetization directions 2532, 2542, 2572similar to first, second and third magnetic layers 2430, 2440, 2470, afirst coupling layer 2520 similar to coupling layer 2420, amagnetoresistive layer 2560 similar to magnetoresistive layer 2460, abody 2512 similar to body 2412 and a circuit 2595 similar to circuit2495.

First magnetization direction 2532 is free, second magnetizationdirection 2542 is free and third magnetization direction 2572 is fixed.First and second magnetic layers 2530, 2540 may be coupled at anorthogonal, non-collinear angle, although this is not necessary. Firstmagnetization direction 2532 has first and second states. In the firstand second states, the X direction orientation of first magnetizationremains constant but the Z direction orientation changes. In otherwords, first magnetization direction 2532 may switch or rotate about anX direction axis to change states. Accordingly, as second magnetizationdirection 2542 switches between stable states, the non-collinear angulardifference between first and second magnetization directions 2532, 2542is not maintained. Instead, second magnetization direction 2542 maytemporarily break free of the non-collinear coupling as it changesbetween stable states. For this reason, second magnetization direction2542 may be less likely to change states undesirably. The stable statesof second magnetization direction 2542 may be more stable (than thestable states of second magnetization direction 2442 of device 2400),since second magnetization direction 2542 must break free of thenon-collinear coupling to change between states.

Third magnetization direction 2572 is depicted as being oriented in thepositive Z direction. This is not mandatory. Third magnetizationdirection 2572 could be oriented in the negative Z direction. Moreover,third magnetization direction 2572 could have an X direction component(and/or a Y direction component). By orienting third magnetizationdirection 2572 without a substantial X direction component, the changesin resistance across body 2512 are greater as second magnetizationdirection 2542 changes states, as compared to if third magnetizationdirection 2572 were to have a substantial X direction component.

First and second magnetization directions 2532, 2542 can be caused tochange between their first and second states by spin torque transfer(e.g. applying a current through circuit 2595). By passing the currentthrough third magnetic layer 2570, the electric current is polarized. Bypassing the polarized current through second magnetic layer 2540, thepolarized current may cause the first and second magnetic layers 2530,2540 to change between stable states. The amount of current for firstand second magnetic layers 2530, 2540 to change states may depend on theangular difference between third magnetization direction 2572 and secondmagnetization direction 2542. The current may be reduced by changing theangular difference between the third magnetization direction 2572 andsecond magnetization direction 2542. Changing the angular differencebetween third magnetization direction 2572 and second magnetizationdirection 2542 may be accomplished with non-collinear coupling (e.g. byemploying magnetic structure 10 and/or coupling layer 25, as describedherein) between first and second magnetic layers 2530, 2540.

FIG. 39C is a schematic diagram of a magnetic device 2600 according to aparticular embodiment. Magnetic device 2600 may be substantially similarto magnetic device 2500 except as described below. Moreover, magneticdevice 2600 may be employed in the same way that magnetic device 2500may be employed as described above and magnetic device 2600 may have thesame (or some of the same) advantages that magnetic device 2500 has asdescribed above in addition to those described below.

Magnetic device 2600 comprises a magnetic structure 2610 similar tomagnetic structure 2510, first, second and third magnetic layers 2630,2640, 2670 having first, second and third magnetization directions 2632,2642, 2672 similar to first, second and third magnetic layers 2530,2540, 2570, a first coupling layer 2620 similar to coupling layer 2520,a first magnetoresistive layer 2660 similar to magnetoresistive layer2560, and a circuit 2695 similar to circuit 2595. Magnetic device 2600also comprises a second magnetoresistive layer 2665 spaced between firstmagnetic layer 2630 and a fourth magnetic layer 2680 having a fourthmagnetization direction 2682. Together, first, second, third and fourthmagnetic layers 2630, 2640, 2670, 2680, first and secondmagnetoresistive layers 2660, 2665 and coupling layer 2620 may bereferred to as body 2612. Like magnetic device 2500, both of first andsecond magnetization directions 2632, 2642 are free and thirdmagnetization direction 2672 is fixed. First and third magnetic layers2632, 2642 may in practice, in combination with coupling layer 2620, actor be treated as one free magnetic layer. Fourth magnetization direction2682 may also be fixed. The addition of second magnetoresistive layer2665 and fourth magnetic layer 2680 may serve to increase the resistivechange across body 2612 of magnetic device 2600 when first and secondmagnetic layers 2630, 2640 change states, decrease switching time, orcurrent for switching (as compared to similar characteristics of device2500).

FIG. 40A to 40D are schematic diagrams of various configurations ofcircuits that may be employed with the magnetic devices described herein(e.g. such as in place of or as part of circuits 195, 295, 395 . . .2495, 2595, 2695, etc.). The FIG. 40A-40D circuits may be used as drivercircuits (e.g. to drive current which may switch the states of one ormore magnetization layer (s)) and/or as measurement circuits (e.g. toevaluate the resistance of a magnetic device). In some embodiments,driver circuits (e.g. circuits used to drive current which may switchstates of one or more magnetization layer(s)) can be embodied separatelyfrom the measurement circuits and/or can be implemented in parallel withthe measurement circuits. The use of the FIG. 40A-40D circuits asmeasurement circuits is described below, it being appreciates thatdriver circuits can be similarly implemented using suitable drivercircuits for current sources and without the need for correspondingvoltmeters.

FIG. 40A depicts a circuit 2795 having first and second leads 2796-1,2796-2 connected between magnetic device 2700 and voltmeter (or suitablevoltage measurement circuit) 2797. Circuit 2795 also comprises third andfourth leads 2798-1, 2798-2 connected between magnetic device 2700 andcurrent source (or suitable current source circuit) 2799. Magneticdevice 2700 may be any magnetic device described herein. Voltmeter 2797may comprise any suitable voltage measuring device or circuit. Currentsource 2799 may be any suitable current source. As can be seen from FIG.40A, first, second, third and fourth leads 2796-1, 2796-2, 2798-1,2798-2 are connected to a first surface 2701 of magnetic device 2700.First surface 2701 may correspond to a magnetic layer, such as, forexample, magnetic layer 170, 270, 670, 990, 1990, etc. that is locatedat a first end of a magnetic device as described herein. In thealternative, first surface 2701 may correspond to a magnetic layer, suchas, for example, magnetic layer 130, 230, 630, 930, 1930, 2380, etc.that is located at a second end of a magnetic device as describedherein. In the alternative, first surface 2701 may correspond to aportion of magnetic device 2700 that is not at the first or second endof a magnetic device such as, for example, magnetic layers 140, 240,730, 740, 1540, 1570, 1980, etc., coupling layers 120, 220, 720, 1520,1920, etc., and/or magnetoresistive layers 160, 260, 760, 1560, 1960,etc.

Although first, second, third and fourth leads 2796-1, 2796-2, 2798-1,2798-2 are depicted as contacting surface 2701 in a particular pattern,this is merely shown for convenience and is not necessary. First,second, third and fourth leads 2796-1, 2796-2, 2798-1, 2798-2 may bearranged in any suitable spatial pattern or configuration on surface2701.

FIG. 40B depicts a circuit 2895 substantially similar to circuit 2795except as described below. Circuit 2895 comprises first and leads2896-1, 2896-2 connected between a first surface 2801 of magnetic device2800 and voltmeter (or suitable voltage measurement circuit) 2897.Circuit 2895 also comprises third and fourth leads 2898-1, 2898-2connected between the first surface 2801 of magnetic device 2800 andcurrent source 2899. Circuit 2895 differs from circuit 2795 in thatthird and fourth leads 2898-1, 2898-2 are connected to surface 2701 viafirst and second leads 2896-1, 2896-2 instead of being connecteddirectly to surface 2801. Circuit 2895 may simplify manufacturing ascompared to circuit 2795 and may be beneficial in embodiments wheresurface 2801 is limited in size.

FIG. 40C depicts a circuit 2995 substantially similar to circuit 2795except as described below. Circuit 2995 comprises a first lead 2996-1connected between a first surface 2901 of magnetic device 2900 andvoltmeter (or suitable voltage measurement circuit) 2997, a second lead2996-2 connected between a second surface 2902 of magnetic device 2900and voltmeter (or suitable voltage measurement circuit) 2997, a thirdlead 2998-1 connected between the first surface 2901 of magnetic device2900 and a current source 2999 and a fourth lead 2998-2 connectedbetween the second surface 2902 of magnetic device 2900 and currentsource 2999. First surface 2901 may correspond to a magnetic layer, suchas, for example, magnetic layer 170, 270, 670, 990, 1990, etc. that islocated at a first end of a magnetic device as described herein. In thealternative, first surface 2901 may correspond to a magnetic layer, suchas, for example, magnetic layer 130, 230, 630, 930, 1930, 2380, etc.that is located at a second end of a magnetic device as describedherein. In the alternative, first surface 2901 may correspond to aportion of magnetic device 2700 that is not at the first or second endof a magnetic device such as, for example, magnetic layers 140, 240,730, 740, 1540, 1570, 1980,etc., coupling layers 120, 220, 720, 1520,1920, etc., and/or magnetoresistive layers 160, 260, 760, 1560, 1960,etc. Similarly, second surface 2902 could comprise a magnetic layer atthe first end of a magnetic device as described herein, comprise amagnetic layer at the second end of a magnetic device as describedherein or to a layer that is not at the first or second end of themagnetic device.

FIG. 40D depicts a circuit 3095 substantially similar to circuit 2995except as described below. Circuit 3095 comprises first and second leads3096-1, 3096-2 connected between first and second surfaces 3001, 3002 ofmagnetic device 3000 respectively and voltmeter (or suitable voltagemeasurement circuit) 3097 and third and fourth leads 3098-1, 3098-2connected between first and second surfaces 3001, 3002 of magneticdevice 3000 respectively and current source 3099. Circuit 3095 differsfrom circuit 2995 in that third and fourth leads 3098-1, 3098-2 areconnected to surfaces 3001, 3002 via first and second leads 3096-1,3096-2 instead of being connected directly to surfaces 3001, 3002.

Various types of current can be driven from current sources 2799, 2899,2999, 3099 through magnetic devices 2700, 2800, 2900, 3000 or any othermagnetic device described herein. For example, the current may compriseDC current, a wave function having, rectangular, triangular, sinusoidaland/or sawtooth like functions and/or the like. The current may bepositive, negative, bipolar, or alternating. The current may bepositively or negatively biased (by suitable DC bias) to a non-zerovalue. For example, the current may be biased to always remain positive,but to maintain a wave function shape having, for example, arectangular, triangular, sinusoidal and/or sawtooth like function.

FIGS. 41A to 41G are schematic depictions of a magnetic device 3100according to a particular embodiment. Magnetic device 3100 comprisesinterior magnetic layer 3170 having an interior magnetization direction3172. An upper magnetic layer 3180 having an upper magnetizationdirection 3182 is spaced apart from interior magnetic layer 3170 by anupper magnetoresistive layer 3165 and a lower magnetic layer 3140 havinga lower magnetization direction 3142 is spaced apart from interiormagnetic layer 3170 by a lower magnetoresistive layer 3160. The termsupper and lower are used merely for convenience and should not beinterpreted as limiting magnetic device 3100 to a particularorientation. Magnetic layers 3140, 3170, 3180 may be substantiallysimilar to other magnetic layers described herein. Magnetoresistivelayers 3160, 3165 may be substantially similar to other magnetoresistivelayers described herein.

Lower magnetization direction 3142 of lower magnetic layer 3140 may befixed in any suitable way that achieves a non-collinear angle betweenlower magnetization direction 3142 and interior magnetization direction3172. Upper magnetization direction 3182 of upper magnetic layer 3180may be fixed in any suitable way that achieves a non-collinear anglebetween upper magnetization direction 3182 and interior magnetizationdirection 3172. For example, lower magnetic layer 3140 and uppermagnetic layer 3180 may each be non-collinearly coupled to additionalmagnetic layers. Such an embodiment is depicted in, for example, FIGS.32B, 33B, 34B and 35B. For example, as compared to the FIG. 32Bembodiment, upper magnetic layer 3180 may correspond to fourth magneticlayer 980, upper magnetoresistive layer 3165 may correspond to secondmagnetoresistive layer 965, interior magnetic layer 3170 may correspondto third magnetic layer 970, lower magnetoresistive layer 3160 maycorrespond to first magnetoresistive layer 960 and lower magnetic layer3140 may correspond to second magnetoresistive layer 940. However, itshould be understood that other suitable techniques could be employed tofix upper and lower magnetization directions 3142, 3182.

As current 3196 passes through magnetic device 3100 in the positive Zdirection as depicted in FIG. 41A, torque of the polarized current thathas passed through lower magnetic layer 3140 may constructivelyinterfere with torque of the current that has reflected from uppermagnetic layer 3180 to increase net the torque on interior magnetizationdirection 3172, thereby decreasing switching time (for a given appliedswitching current) and/or allowing switching of interior magnetizationdirection 3172 with relatively less applied current or applied field.Such constructive interference may be achieved if lower magnetizationdirection 3142 has an X direction and/or Y direction component that isopposite to an X direction and/or Y direction component of uppermagnetization direction 3182. Conversely, if lower magnetizationdirection 3142 has no X direction and/or Y direction component that isopposite to an X direction and/or Y direction component of uppermagnetization direction 3182, then the polarized current that has passedthrough lower magnetic layer 3140 may destructively interfere withcurrent that has reflected from upper magnetic layer 3180, therebyincreasing switching time (for a given applied switching current) and/orrequiring relatively greater current or applied field to allow switchingof interior magnetization direction 3172.

FIGS. 41B to 41G are provided to illustrate a simplified theory of howtorque of the polarized current that has passed through lower magneticlayer 3140 may constructively interfere with torque of the current thathas reflected from upper magnetic layer 3180 to increase the net torqueon interior magnetization direction 3172. FIGS. 41B to 41G are meant tobe illustrative rather than restrictive and the inventors do not wish tobe bound by the simplified theory depicted and described in relation tomagnetic device 3100. It should also be understood that this sameconstructive interference mechanism (or the opposite destructiveinterference mechanism) may be achieved in other magnetic devicesdescribed herein such as, for example, magnetic devices 900, 1100, 1300,1500, 1700, 1900, etc.

Referring to FIG. 41B, as current 3196 passes through lower magneticlayer 3140, current 3196 is polarized in the direction of lowermagnetization direction 3142 as polarized current 3144. Polarizedcurrent 3144 can be described as having an X direction component 3144Aand Z direction component 3144B.

As shown in FIG. 41C, the Z direction component 3144B of polarizedcurrent 3144 passes through interior magnetic layer 3170 as polarizedcurrent 3174 (since interior magnetization direction 3142 is oriented inthe Z direction) while the X direction component 3144A of polarizedcurrent applies a torque 3144A′ on interior magnetization direction3172. A reflected current 3176 is reflected in the opposite direction oftravel of current 3196 (e.g. in the negative Z direction) from interiormagnetic layer 3170 with a polarization direction opposite to interiormagnetization direction 3172.

As shown in FIG. 41D, polarized current 3174 has a first component 3174Aparallel to upper magnetization direction 3182 and a second component3174B orthogonal to upper magnetization direction 3182. Reflectedcurrent 3176 has a first component 3176A parallel to lower magnetizationdirection 3142 and a second component 3176B orthogonal to lowermagnetization direction 3142.

As shown in FIGS. 41E and 41F, second component 3174B of polarizedcurrent 3174 applies a torque 3174B′ on upper magnetization direction3182 and second component 3176B of reflected current 3176 applies atorque 3176B′ on lower magnetization direction 3142.

As shown in FIG. 41F, polarized current 3174 also reflects from uppermagnetic layer 3180 as reflected current 3184. Reflected current 3184has an X direction component 3184A and Z direction component 3184B, asshown in FIG. 41G. The X direction component 3184A of reflected current3184 applies a torque 3184A′ on interior magnetization direction 3172.Due to the opposite X direction components of upper and lowermagnetization directions 3142, 3182, torque 3144A′ and torque 3184A′ areoriented in the same direction (e.g. the negative X direction in theillustrated embodiment) such that they exhibit constructive interferenceand the net torque on interior magnetization direction 3172 isincreased. If, on the other hand, upper and lower magnetizationdirections 3142, 3182 did not have opposite X direction components (anddid not have an opposite Y direction components), torque 3144A′ andtorque 3184A′ would be in opposite directions such that they wouldexhibit destructive interference and the net torque on interiormagnetization direction 3172 would be decreased.

Although, upper and lower magnetization directions 3142, 3182 aredepicted as having Z direction components in the same direction (e.g.positive Z direction), this is not mandatory to achieve constructive ordestructive interference as desired. In some embodiments, upper andlower magnetization directions 3142, 3182 may have Z directioncomponents in opposite directions while still achieving constructive ordestructive interference as desired. In the case of destructiveinteference, the resistance change across magnetic device 3100 between afirst state of interior magnetization direction 3172 and a second stateof interior magnetization direction 3172 may be decreased.

Although upper and lower magnetization directions 3142, 3182 andinterior magnetization direction 3172 are all depicted as having Zdirection components, this is not mandatory. Instead, each of upper andlower magnetization directions 3142, 3182 and interior magnetizationdirection 3172 could extend in XY planes. For example, uppermagnetization direction 3182 could have positive X direction andpositive Y direction components while lower magnetization 3142 directionhas a positive X direction component and a negative Y directioncomponent and interior magnetization direction 3172 has first and secondstable states in the positive and negative Y directions. It should beunderstood that still other combinations of magnetization directions arepossible to achieve constructive interference as desired.

While a number of exemplary aspects and embodiments have been discussedabove, those of skill in the art will recognize certain modifications,permutations, additions and sub-combinations thereof. It is thereforeintended that the following appended claims and claims hereafterintroduced are interpreted to include all such modifications,permutations, additions and sub-combinations as are consistent with thebroadest interpretation of the specification as a whole.

Unless the context clearly requires otherwise, throughout thedescription and any accompanying claims (where present), the words“comprise,” “comprising,” and the like are to be construed in aninclusive sense, that is, in the sense of “including, but not limitedto.” As used herein, the terms “connected,” “coupled,” or any variantthereof, means any connection or coupling, either direct or indirect,between two or more elements; the coupling or connection between theelements can be physical, logical, or a combination thereof.Additionally, the words “herein,” “above,” “below,” and words of similarimport, shall refer to this document as a whole and not to anyparticular portions. Where the context permits, words using the singularor plural number may also include the plural or singular numberrespectively. The word “or,” in reference to a list of two or moreitems, covers all of the following interpretations of the word: any ofthe items in the list, all of the items in the list, and any combinationof the items in the list.

As will be apparent to those skilled in the art in the light of theforegoing disclosure, many alterations and modifications are possible inthe practice of this invention without departing from the spirit orscope thereof. For example:

-   -   Where magnetic layers (and/or magnetization directions) are        discussed herein as being fixed other than by a coupling layer        explicitly recited herein, it should be understood that any        suitable apparatus or method may be employed to fix the        magnetization direction and that devices according to various        embodiments may incorporate such magnetization direction fixing        apparatus or methods to provide the desired fixing. For example,        the material of the magnetic layer may be chosen such that the        magnetization direction is fixed. Alternatively, additional        magnetic layers may be ferromagnetically coupled or coupled by a        coupling layer (e.g. ferromagnetically, antiferromagnetically or        non-collinearly coupled) to the magnetic layer to thereby fix        the magnetization direction.    -   Where a magnetoresistive layer is discussed herein (e.g.        magnetoresistive layer 160, 260, 460, 460 etc.) as being        employed in a sensor (or where it is employed in a sensor), it        should be understood that such magnetoresistive layer is not        mandatory and could be removed entirely without rendering the        magnetic device unsuitable for its purpose.    -   Although some of the drawings herein depict magnetization        directions oriented at approximately 45° with respect to an X        direction axis, a Y direction axis and/or a Z direction axis, it        should be understood that other angles (not including 0, 90,        180, 360) are also suitable and that 45° is depicted for        convenience.    -   Although at least some of the Figures are two-dimensional and do        not show the Y direction dimension, it should be understood that        the magnetic devices depicted do include a Y direction dimension        and the magnetization directions depicted could, but do not        necessarily, have Y direction components unless explicitly        stated otherwise.    -   While some magnetization directions (or components thereof) are        described or shown herein as being in a positive direction, it        should be understood that (with corresponding changes to other        magnetization directions in the structure or device as needed)        such magnetization directions could be negative, and vice versa.    -   While magnetization directions are described herein as, for        example, being oriented in the X direction or in the Z        direction, it should be understood that there may be some        variation between the exact orientation of the magnetization        direction and the stated orientation without departing from the        scope of the invention. For example, in some embodiments, the        angles described herein may be within 2° of the stated        orientation, 5° of the stated orientation, 10° of the stated        orientation, 15° of the stated orientation, or even 20° of the        stated orientation.    -   While in some embodiments, magnetization directions are        discussed as being changed from a first state to a second state        (or to cause a magnetization direction to rotate about an axis)        by spin torque effects or applied current, it should be        understood that an applied magnetic field or a combination of        these may also be employed to change a magnetization direction        from a first state to a second state (or to cause a        magnetization direction to rotate about an axis).    -   While magnetic structures depicted herein may be depicted as        having a constant XY-plane cross-sectional shape and size, this        is not mandatory. Each layer of any of the magnetic structures        described herein may have any XY-plane cross-sectional size or        shape. Further, individual layers are not required to have a        constant XY-plane cross-sectional size or shape along the Z        direction. For example, for device 800, layers 820, 830, 840 may        be 10, 20, 100 or more times larger in XY-plane area than layers        860, 870 which may be on a micrometer or nanometer scale.    -   While some embodiments depicted and/or discussed herein are        discussed as being employed as a sensor and/or a memory device,        it should be understood that such structures may be employed in        other devices such as, for example, oscillators, energy        harvesting devices and diodes.    -   While some embodiments depict structures or devices which        include a free magnetic layer that has only one adjacent layer        (such as magnetic layers 870, 1070, 1270, 1470, 1670, and 1870),        an additional magnetoresistive layer may be interposed between        an additional magnetic layer and the free magnetic layer (such        as magnetic layers 870, 1070, 1270, 1470, 1670, and 1870) to        further amplify torque and/or resistance effects of the device.        The magnetization direction of the additional magnetic layer may        extend in the XY plane or in the Z direction.

What is claimed:
 1. A magnetic device comprising: a first magnetic layerhaving a first magnetization direction; a second magnetic layer having asecond magnetization direction, the second magnetic layer spaced apartfrom the first magnetic layer in the Z direction; a first coupling layerinterposed between the first and second magnetic layers, the firstmagnetic layer non-collinearly coupled to the second magnetic layer bythe first coupling layer such that, in the absence of external magneticfield, the first magnetization direction is oriented at a firstnon-collinear angle relative to the second magnetization direction; athird magnetic layer having a third magnetization direction; a firstmagnetoresistive layer interposed between the third magnetic layer andthe second magnetic layer; and a circuit connected to one or more of thelayers of the magnetic device by at least a pair of leads, the circuitconfigured to determine a change in resistance between the pair ofleads, the change in resistance based at least in part on a change in anangular relationship between the third magnetization direction and thesecond magnetization direction caused by application of an externalmagnetic field in a region where at least a portion of the device islocated or by a current passing through at least a portion of thedevice; wherein an X direction is orthogonal to the Z direction and a Ydirection is orthogonal to the X direction and to the Z direction.
 2. Amagnetic device according to claim 1 wherein the first coupling layercomprises: at least one first non-magnetic element selected from thegroup consisting of: Ag, Cr, Ru, Mo, Ir, Rh, Cu, V, Nb, W, Ta, Ti, Re,Os, Au, Al and Si; and at least one first magnetic element selected fromthe group consisting of: Ni, Co, and Fe; wherein an atomic ratio of theat least one first non-magnetic element to the at least one firstmagnetic element is (100-x):x; and wherein x is an atomic concentrationparameter which causes, or is selected to cause, the first magneticlayer to be non-collinearly coupled to the second magnetic layer.
 3. Amagnetic device according to claim 1 wherein the at least a pair ofleads are connected across the first, second and third magnetic layers,the first coupling layer and the first magnetoresistive layer.
 4. Amagnetic structure according to claim 1 wherein the first non-collinearangle is between approximately 5° and 175° in absence of externalmagnetic field.
 5. A magnetic structure according to claim 1 wherein thefirst non-collinear angle is a non-orthogonal, non-collinear anglebetween approximately 5° and 85° or 95° and 175° in absence of externalmagnetic field.
 6. A magnetic device according to claim 1 wherein thefirst magnetization direction is fixed, the second magnetizationdirection is free and the third magnetization direction is fixed.
 7. Amagnetic device according to claim 1 wherein the first magnetizationdirection is fixed, the second magnetization direction is fixed and thethird magnetization direction is free.
 8. A magnetic device according toclaim 1 wherein the first magnetization direction is free, the secondmagnetization direction is free and the third magnetization direction isfixed.
 9. A magnetic device according to claim 1 comprising a secondcoupling layer interposed between the first magnetic layer and a fourthmagnetic layer, the fourth magnetic layer having a fourth magnetizationdirection.
 10. A magnetic device according to claim 9 wherein the firstmagnetic layer is non-collinearly coupled to the fourth magnetic layersuch that, in the absence of external magnetic field, the firstmagnetization direction is oriented at a second non-collinear anglerelative to the fourth magnetization direction.
 11. A magnetic deviceaccording to claim 9 wherein the fourth magnetization direction isfixed.
 12. A magnetic device according to claim 1 comprising a secondmagnetoresistive layer interposed between the first magnetic layer and afourth magnetic layer, the fourth magnetic layer having a fourthmagnetization direction.
 13. A magnetic device according to claim 12wherein the fourth magnetization direction is fixed.
 14. A magneticdevice according to claim 1 comprising: a second magnetoresistive layerinterposed between a fourth magnetic layer and the third magnetic layer,the fourth magnetic layer having a fourth magnetization direction; and asecond coupling layer interposed between the fourth magnetic layer and afifth magnetic layer, the fifth magnetic layer having a fifthmagnetization direction; wherein the fourth and fifth magnetizationdirections are fixed to one another and wherein the fifth magnetic layeris non-collinearly coupled to the fourth magnetic layer such that, inthe absence of external magnetic field, the fifth magnetizationdirection is oriented at a second non-collinear angle relative to thefourth magnetization direction.
 15. A magnetic device according to claim14 wherein the second and fourth magnetization directions each havenon-zero Z direction components or non-zero Y direction components. 16.A magnetic device according to claim 15 wherein the second magnetizationdirection has an X direction component oriented in the oppositedirection of an X direction component of the fourth magnetizationdirection.
 17. A magnetic device according to claim 15 wherein thesecond magnetization direction has a Z direction component oriented inthe opposite direction of a Z direction component of the fourthmagnetization direction.
 18. A magnetic device according to claim 15wherein the third magnetization direction is parallel to the Zdirection.
 19. A magnetic device according to claim 15 wherein the thirdmagnetization direction extends in a plane defined by the X and Ydirections.
 20. A magnetic device according to claim 1 wherein at leasta portion of the magnetic device has an X direction dimension that isgreater than a Y direction dimension of the at least a portion of themagnetic device.
 21. A magnetic device according to claim 1 wherein atleast a portion of the magnetic device has an X direction dimension thatis substantially equal to a Y direction dimension of the at least aportion of the magnetic device.
 22. A magnetic device comprising: anupper magnetic layer having an upper magnetization direction; a lowermagnetic layer having a lower magnetization direction, the lowermagnetic layer spaced apart from the upper magnetic layer in a Zdirection; an interior magnetic layer having an interior magnetizationdirection; a lower magnetoresistive layer interposed between the lowermagnetic layer and the interior magnetic layer; an uppermagnetoresistive layer interposed between the upper magnetic layer andthe free magnetic layer; a circuit connected to one or more of thelayers of the magnetic device by at least a pair of leads, the circuitconfigured to determine a change in resistance between the pair ofleads, the change in resistance based at least in part on a change in anangular relationship between the upper magnetization direction and theinterior magnetization and an angular relationship between the lowermagnetization direction and the interior magnetization direction causedby application of an external magnetic field in a region where at leasta portion of the device is located or by a current passing through atleast a portion of the device; wherein: an X direction is orthogonal tothe Z direction and a Y direction is orthogonal to the X direction andto the Z direction; the upper and lower magnetization directions areeach fixed and the interior magnetization direction is free; the upperand lower magnetization directions each have non-zero Z directioncomponents or non-zero Y components; and the upper magnetizationdirection has an X direction component oriented in the oppositedirection of an X direction component of the lower magnetizationdirection.
 23. A magnetic memory device comprising: a magnetic deviceaccording to claim 1; wherein the change in resistance is based at leastin part on the change in the angular relationship between the thirdmagnetization direction and the second magnetization direction caused bya current passing through at least a portion of the device.
 24. Amagnetic memory device according to claim 23 wherein the change in theangular relationship between the third magnetization direction and thesecond magnetization comprises a change between a first staterepresenting a first value for a bit of information and a second staterepresenting a second value for the bit of information.
 25. A magneticsensor device comprising: a magnetic device according to claim 1;wherein the change in resistance is based at least in part on the changein the angular relationship between the third magnetization directionand the second magnetization direction caused by the application of theexternal magnetic field.
 26. An oscillator device comprising: a magneticdevice according to claim 1; wherein a driver circuit is connected toone or more of the layers of the magnetic device to apply driver currentto the magnetic device to create, in the circuit, a signal based atleast in part on the angular relationship between the thirdmagnetization direction and the second magnetization direction.
 27. Amethod of sensing an external field with a magnetic sensor device, themethod comprising: providing an oscillator device according to claim 26;applying an external field to the oscillator device; measuring thesignal; associating a measurement of the signal with the presence of theexternal field.
 28. A method of storing information on a magnetic memorydevice, the method comprising: providing a magnetic device according toclaim 1; applying a current through at least a portion of the device tochange the angular relationship between the third magnetizationdirection and the second magnetization direction; measuring theresistance of the magnetic device to determine the angular relationshipbetween the third magnetization direction and the second magnetizationdirection; associating a measured relationship between the thirdmagnetization direction and the second magnetization direction with avalue of a bit of information.
 29. A method of sensing an external fieldwith a magnetic sensor device, the method comprising: providing amagnetic device according to claim 1; applying an external field to themagnetic device; measuring the resistance of the magnetic device todetermine the angular relationship between the third magnetizationdirection and the second magnetization direction; associating a measuredrelationship between the third magnetization direction and the secondmagnetization direction with the presence of the external field.
 30. Amethod of creating an alternating current output signal from a directcurrent input signal, the method comprising: providing a magnetic deviceaccording to claim 1; applying a direct current input signal through oneor more layers of the magnetic device to continuously change the angularrelationship between the third magnetization direction and the secondmagnetization direction; receiving an alternating current output signalbased at least in part on the continuous change of the angularrelationship between the third magnetization direction and the secondmagnetization direction.
 31. A method of creating a direct currentoutput signal from an alternating current input signal, the methodcomprising: providing a magnetic device according to claim 1; applyingan alternating current input signal through one or more layers of themagnetic device to continuously change the angular relationship betweenthe third magnetization direction and the second magnetizationdirection; receiving a direct current output signal based at least inpart on the continuous change of the angular relationship between thethird magnetization direction and the second magnetization direction.